diff --git a/.changes/next-release/bugfix-AmazonDynamoDBEnhancedClient-192189d.json b/.changes/next-release/bugfix-AmazonDynamoDBEnhancedClient-192189d.json
new file mode 100644
index 00000000000..549092a8a4a
--- /dev/null
+++ b/.changes/next-release/bugfix-AmazonDynamoDBEnhancedClient-192189d.json
@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "Amazon DynamoDB Enhanced Client",
+    "contributor": "",
+    "description": "Fix NullPointerException in `DoubleAttributeConverter` and `FloatAttributeConverter` when input is null. Fixes [#6639](https://github.com/aws/aws-sdk-java-v2/issues/6639)."
+}
diff --git a/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/ConverterUtils.java b/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/ConverterUtils.java
index 0f6f2058318..303a3c70313 100644
--- a/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/ConverterUtils.java
+++ b/services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/ConverterUtils.java
@@ -39,6 +39,7 @@ private ConverterUtils() {
      * @param input
      */
     public static void validateDouble(Double input) {
+        Validate.paramNotNull(input, "input");
         Validate.isTrue(!Double.isNaN(input), "NaN is not supported by the default converters.");
         Validate.isTrue(Double.isFinite(input), "Infinite numbers are not supported by the default converters.");
     }
@@ -48,6 +49,7 @@ public static void validateDouble(Double input) {
      * @param input
      */
     public static void validateFloat(Float input) {
+        Validate.paramNotNull(input, "input");
         Validate.isTrue(!Float.isNaN(input), "NaN is not supported by the default converters.");
         Validate.isTrue(Float.isFinite(input), "Infinite numbers are not supported by the default converters.");
     }
diff --git a/services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/converters/attribute/NumberAttributeConvertersTest.java b/services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/converters/attribute/NumberAttributeConvertersTest.java
index bfbbf0ca608..172db359120 100644
--- a/services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/converters/attribute/NumberAttributeConvertersTest.java
+++ b/services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/converters/attribute/NumberAttributeConvertersTest.java
@@ -16,6 +16,7 @@
 package software.amazon.awssdk.enhanced.dynamodb.converters.attribute;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import static org.assertj.core.data.Offset.offset;
 import static software.amazon.awssdk.enhanced.dynamodb.converters.attribute.ConverterTestUtils.assertFails;
 import static software.amazon.awssdk.enhanced.dynamodb.converters.attribute.ConverterTestUtils.transformFrom;
@@ -150,6 +151,9 @@ public void floatAttributeConverterBehaves() {
         assertFails(() -> transformFrom(converter, Float.NEGATIVE_INFINITY));
         assertFails(() -> transformFrom(converter, Float.POSITIVE_INFINITY));
         assertFails(() -> transformFrom(converter, Float.NaN));
+        assertThatThrownBy(() -> transformFrom(converter, null))
+            .isInstanceOf(NullPointerException.class)
+            .hasMessageContaining("input must not be null");
 
         assertThat(transformFrom(converter, -Float.MAX_VALUE).n()).isEqualTo("-3.4028235E38");
         assertThat(Float.parseFloat(transformFrom(converter, -42.42f).n())).isCloseTo(-42.42f, offset(1E-10f));
@@ -179,6 +183,9 @@ public void doubleAttributeConverterBehaves() {
         assertFails(() -> transformFrom(converter, Double.NEGATIVE_INFINITY));
         assertFails(() -> transformFrom(converter, Double.POSITIVE_INFINITY));
         assertFails(() -> transformFrom(converter, Double.NaN));
+        assertThatThrownBy(() -> transformFrom(converter, null))
+            .isInstanceOf(NullPointerException.class)
+            .hasMessageContaining("input must not be null");
 
         assertThat(transformFrom(converter, -Double.MAX_VALUE).n()).isEqualTo("-1.7976931348623157E308");
         assertThat(Double.parseDouble(transformFrom(converter, -42.42d).n())).isCloseTo(-42.42d, offset(1E-10));