diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index d9b3963b8..59a1ae9b2 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -42,6 +42,7 @@
   <body>
     <release version="1.15.0" date="YYYY-MM-DD" description="This is a feature and maintenance release. Java 8 or later is required.">
       <!-- FIX -->
+      <action type="fix" issue="CSV-330" due-to="Aryan Ganjoo">CSVRecord.isConsistent() compares against the number of header columns when duplicate or empty header names are allowed.</action>
       <action type="fix" issue="CSV-320" dev="aherbert" due-to="Jan Burkhardt">Remove Spotbugs dependency and use exclude-filter instead #564.</action>
       <action type="fix" dev="ggregory" due-to="Cassio Santos">Remove broken website link #577.</action>
       <action type="fix" dev="ggregory" due-to="Gary Gregory">Fix Apache RAT plugin console warnings.</action>
diff --git a/src/main/java/org/apache/commons/csv/CSVParser.java b/src/main/java/org/apache/commons/csv/CSVParser.java
index eb4c0d329..06d3a6d6f 100644
--- a/src/main/java/org/apache/commons/csv/CSVParser.java
+++ b/src/main/java/org/apache/commons/csv/CSVParser.java
@@ -308,9 +308,15 @@ private static final class Headers {
          */
         final List<String> headerNames;
 
-        Headers(final Map<String, Integer> headerMap, final List<String> headerNames) {
+        /**
+         * Number of header columns, including duplicate and null names that do not add a distinct entry to {@link #headerMap}.
+         */
+        final int headerCount;
+
+        Headers(final Map<String, Integer> headerMap, final List<String> headerNames, final int headerCount) {
             this.headerMap = headerMap;
             this.headerNames = headerNames;
+            this.headerCount = headerCount;
         }
     }
 
@@ -628,6 +634,7 @@ private Map<String, Integer> createEmptyHeaderMap() {
     private Headers createHeaders() throws IOException {
         Map<String, Integer> headerMap = null;
         List<String> headerNames = null;
+        int headerCount = 0;
         final String[] formatHeader = format.getHeader();
         if (formatHeader != null) {
             headerMap = createEmptyHeaderMap();
@@ -650,6 +657,7 @@ private Headers createHeaders() throws IOException {
             }
             // build the name to index mappings
             if (headerRecord != null) {
+                headerCount = headerRecord.length;
                 // Track an occurrence of a null, empty or blank header.
                 boolean observedMissing = false;
                 for (int i = 0; i < headerRecord.length; i++) {
@@ -679,7 +687,7 @@ private Headers createHeaders() throws IOException {
             }
         }
         // Make header names Collection immutable
-        return new Headers(headerMap, headerNames == null ? Collections.emptyList() : Collections.unmodifiableList(headerNames));
+        return new Headers(headerMap, headerNames == null ? Collections.emptyList() : Collections.unmodifiableList(headerNames), headerCount);
     }
 
     /**
@@ -747,6 +755,15 @@ Map<String, Integer> getHeaderMapRaw() {
         return headers.headerMap;
     }
 
+    /**
+     * Gets the number of header columns, which can exceed the header map size when duplicate or null names are allowed.
+     *
+     * @return The number of header columns.
+     */
+    int getHeaderCount() {
+        return headers.headerCount;
+    }
+
     /**
      * Gets a read-only list of header names that iterates in column order as defined in the CSVFormat's header.
      * <p>
diff --git a/src/main/java/org/apache/commons/csv/CSVRecord.java b/src/main/java/org/apache/commons/csv/CSVRecord.java
index 9e8071379..2de2fe315 100644
--- a/src/main/java/org/apache/commons/csv/CSVRecord.java
+++ b/src/main/java/org/apache/commons/csv/CSVRecord.java
@@ -235,8 +235,9 @@ public boolean hasComment() {
      * @return true of this record is valid, false if not.
      */
     public boolean isConsistent() {
-        final Map<String, Integer> headerMap = getHeaderMapRaw();
-        return headerMap == null || headerMap.size() == values.length;
+        // Compare with the header column count, not the header map size: duplicate or null header names allowed by
+        // DuplicateHeaderMode or allowMissingColumnNames share or lack a map entry.
+        return getHeaderMapRaw() == null || parser.getHeaderCount() == values.length;
     }
 
     /**
diff --git a/src/test/java/org/apache/commons/csv/CSVRecordTest.java b/src/test/java/org/apache/commons/csv/CSVRecordTest.java
index 821532975..344ac14c5 100644
--- a/src/test/java/org/apache/commons/csv/CSVRecordTest.java
+++ b/src/test/java/org/apache/commons/csv/CSVRecordTest.java
@@ -194,14 +194,39 @@ void testIsConsistent() {
         assertTrue(recordWithHeader.isConsistent());
     }
 
+    /**
+     * A record whose size matches the header column count is consistent even when duplicate header names share a
+     * single header map entry.
+     */
+    @Test
+    void testIsConsistentWithDuplicateHeaderNames() throws IOException {
+        final CSVFormat format = CSVFormat.DEFAULT.builder().setHeader().setDuplicateHeaderMode(DuplicateHeaderMode.ALLOW_ALL).get();
+        try (CSVParser parser = format.parse(new StringReader("a,b,a\n1,2,3\n1,2\n"))) {
+            final List<CSVRecord> records = parser.getRecords();
+            assertTrue(records.get(0).isConsistent());
+            assertFalse(records.get(1).isConsistent());
+        }
+    }
+
+    /**
+     * A record whose size matches the header column count is consistent even when empty header names share a single
+     * header map entry.
+     */
+    @Test
+    void testIsConsistentWithDuplicateEmptyHeaderNames() throws IOException {
+        final CSVFormat format = CSVFormat.DEFAULT.builder().setHeader().setAllowMissingColumnNames(true)
+                .setDuplicateHeaderMode(DuplicateHeaderMode.ALLOW_EMPTY).get();
+        try (CSVParser parser = format.parse(new StringReader("a,,b,\n1,2,3,4\n"))) {
+            assertTrue(parser.nextRecord().isConsistent());
+        }
+    }
+
     @Test
     void testIsInconsistent() throws IOException {
-        final String[] headers = { "first", "second", "third" };
+        final String[] headers = { "first", "second", "third", "fourth" };
         final String rowData = StringUtils.join(values, ',');
         try (CSVParser parser = CSVFormat.DEFAULT.withHeader(headers).parse(new StringReader(rowData))) {
-            final Map<String, Integer> map = parser.getHeaderMapRaw();
             final CSVRecord record1 = parser.iterator().next();
-            map.put("fourth", Integer.valueOf(4));
             assertFalse(record1.isConsistent());
         }
     }