diff --git a/src/main/java/io/github/jopenlibs/vault/api/pki/Pki.java b/src/main/java/io/github/jopenlibs/vault/api/pki/Pki.java
index 24b288e..312304f 100644
--- a/src/main/java/io/github/jopenlibs/vault/api/pki/Pki.java
+++ b/src/main/java/io/github/jopenlibs/vault/api/pki/Pki.java
@@ -329,7 +329,110 @@ public PkiResponse issue(
             final String ttl,
             final CredentialFormat format) throws VaultException {
 
-        return issue(roleName, commonName, altNames, ipSans, ttl, format, "");
+        return issue(roleName, commonName, altNames, ipSans, ttl, format, "", PrivateKeyFormat.DER);
+    }
+
+    /**
+     * <p>Operation to generate a new set of credentials (private key and certificate) based on a
+     * given role using the PKI backend.  The issuing CA certificate is returned as well, so that
+     * only the root CA need be in a client's trust store.</p>
+     *
+     * <p>A successful operation will return a 204 HTTP status.  A <code>VaultException</code> will
+     * be thrown if the role does not exist, or if any other problem occurs.  Credential information
+     * will be populated in the <code>credential</code> field of the <code>PkiResponse</code> return
+     * value. Example usage:</p>
+     *
+     * <blockquote>
+     * <pre>{@code
+     * final VaultConfig config = new VaultConfig.address(...).token(...).build();
+     * final Vault vault = Vault.create(config);
+     *
+     * final PkiResponse response = vault.pki().deleteRole("testRole");
+     * assertEquals(204, response.getRestResponse().getStatus();
+     * }</pre>
+     * </blockquote>
+     *
+     * @param roleName The role on which the credentials will be based.
+     * @param commonName The requested CN for the certificate. If the CN is allowed by role policy,
+     * it will be issued.
+     * @param altNames (optional) Requested Subject Alternative Names, in a comma-delimited list.
+     * These can be host names or email addresses; they will be parsed into their respective fields.
+     * If any requested names do not match role policy, the entire request will be denied.
+     * @param ipSans (optional) Requested IP Subject Alternative Names, in a comma-delimited list.
+     * Only valid if the role allows IP SANs (which is the default).
+     * @param ttl (optional) Requested Time To Live. Cannot be greater than the role's max_ttl
+     * value. If not provided, the role's ttl value will be used. Note that the role values default
+     * to system values if not explicitly set.
+     * @param format (optional) Format for returned data. Can be pem, der, or pem_bundle; defaults
+     * to pem. If der, the output is base64 encoded. If pem_bundle, the certificate field will
+     * contain the private key, certificate, and issuing CA, concatenated.
+     * @param privateKeyFormat (optional) Specifies the format for marshaling the
+     * private key. Defaults to `der` which will return either base64-encoded DER or
+     * PEM-encoded DER, depending on the value of `format`. The other option is
+     * `pkcs8` which will return the key marshalled as PEM-encoded PKCS8
+     * @return A container for the information returned by Vault
+     * @throws VaultException If any error occurs or unexpected response is received from Vault
+     */
+    public PkiResponse issue(
+            final String roleName,
+            final String commonName,
+            final List<String> altNames,
+            final List<String> ipSans,
+            final String ttl,
+            final CredentialFormat format,
+            final PrivateKeyFormat privateKeyFormat) throws VaultException {
+
+        return issue(roleName, commonName, altNames, ipSans, ttl, format, "", privateKeyFormat);
+    }
+
+    /**
+     * <p>Operation to generate a new set of credentials (private key and certificate) based on a
+     * given role using the PKI backend.  The issuing CA certificate is returned as well, so that
+     * only the root CA need be in a client's trust store.</p>
+     *
+     * <p>A successful operation will return a 204 HTTP status.  A <code>VaultException</code> will
+     * be thrown if the role does not exist, or if any other problem occurs.  Credential information
+     * will be populated in the <code>credential</code> field of the <code>PkiResponse</code> return
+     * value. Example usage:</p>
+     *
+     * <blockquote>
+     * <pre>{@code
+     * final VaultConfig config = new VaultConfig.address(...).token(...).build();
+     * final Vault vault = Vault.create(config);
+     *
+     * final PkiResponse response = vault.pki().deleteRole("testRole");
+     * assertEquals(204, response.getRestResponse().getStatus();
+     * }</pre>
+     * </blockquote>
+     *
+     * @param roleName The role on which the credentials will be based.
+     * @param commonName The requested CN for the certificate. If the CN is allowed by role policy,
+     * it will be issued.
+     * @param altNames (optional) Requested Subject Alternative Names, in a comma-delimited list.
+     * These can be host names or email addresses; they will be parsed into their respective fields.
+     * If any requested names do not match role policy, the entire request will be denied.
+     * @param ipSans (optional) Requested IP Subject Alternative Names, in a comma-delimited list.
+     * Only valid if the role allows IP SANs (which is the default).
+     * @param ttl (optional) Requested Time To Live. Cannot be greater than the role's max_ttl
+     * value. If not provided, the role's ttl value will be used. Note that the role values default
+     * to system values if not explicitly set.
+     * @param format (optional) Format for returned data. Can be pem, der, or pem_bundle; defaults
+     * to pem. If der, the output is base64 encoded. If pem_bundle, the certificate field will
+     * contain the private key, certificate, and issuing CA, concatenated.
+     * @param csr (optional) PEM Encoded CSR
+     * @return A container for the information returned by Vault
+     * @throws VaultException If any error occurs or unexpected response is received from Vault
+     */
+    public PkiResponse issue(
+            final String roleName,
+            final String commonName,
+            final List<String> altNames,
+            final List<String> ipSans,
+            final String ttl,
+            final CredentialFormat format,
+            final String csr) throws VaultException {
+
+        return issue(roleName, commonName, altNames, ipSans, ttl, format, csr, PrivateKeyFormat.DER);
     }
 
     /**
@@ -369,6 +472,10 @@ public PkiResponse issue(
      * to pem. If der, the output is base64 encoded. If pem_bundle, the certificate field will
      * contain the private key, certificate, and issuing CA, concatenated.
      * @param csr (optional) PEM Encoded CSR
+     * @param privateKeyFormat (optional) Specifies the format for marshaling the
+     * private key. Defaults to `der` which will return either base64-encoded DER or
+     * PEM-encoded DER, depending on the value of `format`. The other option is
+     * `pkcs8` which will return the key marshalled as PEM-encoded PKCS8
      * @return A container for the information returned by Vault
      * @throws VaultException If any error occurs or unexpected response is received from Vault
      */
@@ -379,7 +486,8 @@ public PkiResponse issue(
             final List<String> ipSans,
             final String ttl,
             final CredentialFormat format,
-            final String csr
+            final String csr,
+            final PrivateKeyFormat privateKeyFormat
     ) throws VaultException {
         return retry(attempt -> {
             // Construct a JSON body from inputs
@@ -419,6 +527,10 @@ public PkiResponse issue(
                 jsonObject.add("format", format.toString());
             }
 
+            if(privateKeyFormat != null) {
+                jsonObject.add("private_key_format", privateKeyFormat.toString());
+            }
+
             if (csr != null) {
                 jsonObject.add("csr", csr);
             }
diff --git a/src/main/java/io/github/jopenlibs/vault/api/pki/PrivateKeyFormat.java b/src/main/java/io/github/jopenlibs/vault/api/pki/PrivateKeyFormat.java
new file mode 100644
index 0000000..ededc3c
--- /dev/null
+++ b/src/main/java/io/github/jopenlibs/vault/api/pki/PrivateKeyFormat.java
@@ -0,0 +1,29 @@
+package io.github.jopenlibs.vault.api.pki;
+
+import java.util.List;
+
+/**
+ * <p>Possible format options for private key issued by the PKI backend.</p>
+ *
+ * <p>See: {@link Pki#issue(String, String, List, List, String, CredentialFormat)}</p>
+ */
+public enum PrivateKeyFormat {
+    DER,
+    PKCS8;
+
+    public static PrivateKeyFormat fromString(final String text) {
+        if (text != null) {
+            for (final PrivateKeyFormat format : PrivateKeyFormat.values()) {
+                if (text.equalsIgnoreCase(format.toString())) {
+                    return format;
+                }
+            }
+        }
+        return null;
+    }
+
+    @Override
+    public String toString() {
+        return super.toString().toLowerCase();
+    }
+}
diff --git a/src/test-integration/java/io/github/jopenlibs/vault/api/AuthBackendPkiTests.java b/src/test-integration/java/io/github/jopenlibs/vault/api/AuthBackendPkiTests.java
index f653691..347c20a 100644
--- a/src/test-integration/java/io/github/jopenlibs/vault/api/AuthBackendPkiTests.java
+++ b/src/test-integration/java/io/github/jopenlibs/vault/api/AuthBackendPkiTests.java
@@ -3,6 +3,8 @@
 import io.github.jopenlibs.vault.Vault;
 import io.github.jopenlibs.vault.VaultException;
 import io.github.jopenlibs.vault.api.pki.CredentialFormat;
+import io.github.jopenlibs.vault.api.pki.Pki;
+import io.github.jopenlibs.vault.api.pki.PrivateKeyFormat;
 import io.github.jopenlibs.vault.api.pki.RoleOptions;
 import io.github.jopenlibs.vault.response.PkiResponse;
 import io.github.jopenlibs.vault.rest.RestResponse;
@@ -16,6 +18,8 @@
 import java.security.PrivateKey;
 import java.security.PublicKey;
 import java.util.ArrayList;
+import java.util.function.BiFunction;
+import java.util.function.Function;
 import junit.framework.TestCase;
 import org.junit.Before;
 import org.junit.BeforeClass;
@@ -82,8 +86,7 @@ public void testDeleteRole() throws VaultException {
         TestCase.assertEquals(404, getResponse.getRestResponse().getStatus());
     }
 
-    @Test
-    public void testIssueCredential() throws VaultException, InterruptedException {
+    void issueCredentialTemplate(Function<Pki, PkiResponse> pkiResponseFunction) throws VaultException, InterruptedException {
         final Vault vault = container.getRootVault();
 
         // Create a role
@@ -101,8 +104,7 @@ public void testIssueCredential() throws VaultException, InterruptedException {
         Thread.sleep(3000);
 
         // Issue cert
-        final PkiResponse issueResponse = vault.pki()
-                .issue("testRole", "test.myvault.com", null, null, "1h", CredentialFormat.PEM);
+        final PkiResponse issueResponse = pkiResponseFunction.apply(vault.pki());
         TestCase.assertNotNull(issueResponse.getCredential().getCertificate());
         TestCase.assertNotNull(issueResponse.getCredential().getPrivateKey());
         TestCase.assertNotNull(issueResponse.getCredential().getSerialNumber());
@@ -111,8 +113,31 @@ public void testIssueCredential() throws VaultException, InterruptedException {
     }
 
     @Test
-    public void testIssueCredentialWithCsr()
-            throws VaultException, InterruptedException, NoSuchAlgorithmException {
+    public void testIssueCredential() throws VaultException, InterruptedException {
+        issueCredentialTemplate(pki -> {
+            try {
+                return pki.issue("testRole", "test.myvault.com", null, null, "1h", CredentialFormat.PEM);
+            } catch (VaultException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+    }
+
+    @Test
+    public void testIssueCredentialWithPrivateKeyFormat() throws VaultException, InterruptedException {
+        issueCredentialTemplate(pki -> {
+            try {
+                return pki.issue("testRole", "test.myvault.com", null, null, "1h", CredentialFormat.PEM, PrivateKeyFormat.PKCS8);
+            } catch (VaultException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+    }
+
+    void issueCredentialWithCsrTemplate(BiFunction<Pki, String, PkiResponse> pkiResponseFunction)
+            throws VaultException, InterruptedException, NoSuchAlgorithmException  {
 
         KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
         kpg.initialize(2048);
@@ -142,14 +167,40 @@ public void testIssueCredentialWithCsr()
         Thread.sleep(3000);
 
         // Issue cert
-        final PkiResponse issueResponse = vault.pki()
-                .issue("testRole", "test.myvault.com", null, null, "1h", CredentialFormat.PEM, csr);
+        final PkiResponse issueResponse = pkiResponseFunction.apply(vault.pki(), csr);
         TestCase.assertNotNull(issueResponse.getCredential().getCertificate());
         TestCase.assertNotNull(issueResponse.getCredential().getCaChain());
         TestCase.assertNull(issueResponse.getCredential().getPrivateKey());
         TestCase.assertNotNull(issueResponse.getCredential().getSerialNumber());
         TestCase.assertNotNull(issueResponse.getCredential().getIssuingCa());
     }
+    @Test
+    public void testIssueCredentialWithCsr()
+            throws VaultException, InterruptedException, NoSuchAlgorithmException {
+
+        issueCredentialWithCsrTemplate((pki, csr) -> {
+            try {
+                return pki.issue("testRole", "test.myvault.com", null, null, "1h", CredentialFormat.PEM, csr);
+            } catch (VaultException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+    }
+
+    @Test
+    public void testIssueCredentialWithCsrAndPrivateKeyFormat()
+            throws VaultException, InterruptedException, NoSuchAlgorithmException {
+
+        issueCredentialWithCsrTemplate((pki, csr) -> {
+            try {
+                return pki.issue("testRole", "test.myvault.com", null, null, "1h", CredentialFormat.PEM, csr, PrivateKeyFormat.PKCS8);
+            } catch (VaultException e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+    }
 
     @Test
     public void testRevocation() throws VaultException, InterruptedException {