diff --git a/pre_commit_hooks/check_json.py b/pre_commit_hooks/check_json.py
index 6a679fee..51e0f21c 100644
--- a/pre_commit_hooks/check_json.py
+++ b/pre_commit_hooks/check_json.py
@@ -2,8 +2,8 @@
 
 import argparse
 import json
-from typing import Any
-from typing import Sequence
+import re
+from typing import Any, Sequence
 
 
 def raise_duplicate_keys(
@@ -17,6 +17,29 @@ def raise_duplicate_keys(
             d[key] = val
     return d
 
+def check_mixed_indentation(content: str, filename: str) -> bool:
+    """
+    Checks a string content for mixed indentation (tabs and spaces) in leading whitespace.
+
+    Args:
+        content (str): The content of the file to check.
+        filename (str): The name of the file being checked (for reporting purposes).
+
+    Returns:
+        bool: True if mixed indentation is found, False otherwise.
+    """
+    found_mixed = False
+
+    for i, line in enumerate(content.splitlines(), 1):
+        # Determine leading whitespace
+        leading_whitespace = line[:len(line) - len(line.lstrip())]
+
+        # Check if both tabs and spaces are present in leading whitespace
+        if ' ' in leading_whitespace and '\t' in leading_whitespace:
+            print(f"{filename}: Mixed indentation (tabs and spaces) found on line {i}")
+            found_mixed = True
+
+    return not found_mixed
 
 def main(argv: Sequence[str] | None = None) -> int:
     parser = argparse.ArgumentParser()
@@ -25,12 +48,21 @@ def main(argv: Sequence[str] | None = None) -> int:
 
     retval = 0
     for filename in args.filenames:
-        with open(filename, 'rb') as f:
-            try:
-                json.load(f, object_pairs_hook=raise_duplicate_keys)
-            except ValueError as exc:
-                print(f'{filename}: Failed to json decode ({exc})')
-                retval = 1
+        with open(filename, 'r') as f:
+            content = f.read()
+
+        # Check for mixed indentation first
+        if not check_mixed_indentation(content, filename):
+            retval = 1
+            continue
+
+        # Then, attempt to parse the JSON
+        try:
+            json.loads(content, object_pairs_hook=raise_duplicate_keys)
+        except ValueError as exc:
+            print(f'{filename}: Failed to json decode ({exc})')
+            retval = 1
+
     return retval