diff --git a/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/DataMongoProperties.java b/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/DataMongoProperties.java
index 7f8f3491264..40e31ead5c1 100644
--- a/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/DataMongoProperties.java
+++ b/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/DataMongoProperties.java
@@ -103,13 +103,13 @@ public class DataMongoProperties {
 		/**
 		 * Representation to use when converting a BigDecimal.
 		 */
-		private BigDecimalRepresentation bigDecimal = BigDecimalRepresentation.DECIMAL128;
+		private @Nullable BigDecimalRepresentation bigDecimal;
 
-		public BigDecimalRepresentation getBigDecimal() {
+		public @Nullable BigDecimalRepresentation getBigDecimal() {
 			return this.bigDecimal;
 		}
 
-		public void setBigDecimal(BigDecimalRepresentation bigDecimal) {
+		public void setBigDecimal(@Nullable BigDecimalRepresentation bigDecimal) {
 			this.bigDecimal = bigDecimal;
 		}
 
diff --git a/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataConfiguration.java b/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataConfiguration.java
index 7171c6fb4a2..ed199cd8dd2 100644
--- a/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataConfiguration.java
+++ b/module/spring-boot-data-mongodb/src/main/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataConfiguration.java
@@ -32,6 +32,7 @@ import org.springframework.data.mongodb.core.convert.DefaultDbRefResolver;
 import org.springframework.data.mongodb.core.convert.MappingMongoConverter;
 import org.springframework.data.mongodb.core.convert.MongoConverter;
 import org.springframework.data.mongodb.core.convert.MongoCustomConversions;
+import org.springframework.data.mongodb.core.convert.MongoCustomConversions.BigDecimalRepresentation;
 import org.springframework.data.mongodb.core.convert.NoOpDbRefResolver;
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.data.mongodb.core.mapping.MongoMappingContext;
@@ -76,8 +77,12 @@ class MongoDataConfiguration {
 	@Bean
 	@ConditionalOnMissingBean
 	MongoCustomConversions mongoCustomConversions() {
-		return MongoCustomConversions
-			.create((configurer) -> configurer.bigDecimal(this.properties.getRepresentation().getBigDecimal()));
+		return MongoCustomConversions.create((configurer) -> {
+			BigDecimalRepresentation bigDecimaRepresentation = this.properties.getRepresentation().getBigDecimal();
+			if (bigDecimaRepresentation != null) {
+				configurer.bigDecimal(bigDecimaRepresentation);
+			}
+		});
 	}
 
 	@Bean
diff --git a/module/spring-boot-data-mongodb/src/test/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataAutoConfigurationTests.java b/module/spring-boot-data-mongodb/src/test/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataAutoConfigurationTests.java
index ed0a389bc1d..016209abff7 100644
--- a/module/spring-boot-data-mongodb/src/test/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataAutoConfigurationTests.java
+++ b/module/spring-boot-data-mongodb/src/test/java/org/springframework/boot/data/mongodb/autoconfigure/MongoDataAutoConfigurationTests.java
@@ -119,7 +119,8 @@ class MongoDataAutoConfigurationTests {
 	}
 
 	@Test
-	void customBigDecimalRepresentation() {
+	@Deprecated(since = "4.0.0")
+	void customBigDecimalDeprecatedRepresentation() {
 		this.contextRunner.withPropertyValues("spring.data.mongodb.representation.big-decimal=string")
 			.run((context) -> assertThat(context.getBean(MongoCustomConversions.class)).extracting("converters")
 				.asInstanceOf(InstanceOfAssertFactories.LIST)
@@ -128,14 +129,25 @@ class MongoDataAutoConfigurationTests {
 				.anySatisfy((className) -> assertThat(className).contains("BigIntegerToStringConverter")));
 	}
 
+	@Test
+	void customBigDecimalRepresentation() {
+		this.contextRunner.withPropertyValues("spring.data.mongodb.representation.big-decimal=decimal128")
+			.run((context) -> assertThat(context.getBean(MongoCustomConversions.class)).extracting("converters")
+				.asInstanceOf(InstanceOfAssertFactories.LIST)
+				.map((converter) -> converter.getClass().getName())
+				.anySatisfy((className) -> assertThat(className).contains("BigDecimalToDecimal128Converter"))
+				.anySatisfy((className) -> assertThat(className).contains("BigIntegerToDecimal128Converter")));
+	}
+
 	@Test
 	void defaultBigDecimalRepresentation() {
 		this.contextRunner
 			.run((context) -> assertThat(context.getBean(MongoCustomConversions.class)).extracting("converters")
 				.asInstanceOf(InstanceOfAssertFactories.LIST)
 				.map((converter) -> converter.getClass().getName())
-				.noneSatisfy((className) -> assertThat(className).contains("BigDecimalToStringConverter"))
-				.noneSatisfy((className) -> assertThat(className).contains("BigIntegerToStringConverter")));
+				.filteredOn((className) -> className.startsWith("org.springframework.data.mongodb"))
+				.noneSatisfy((className) -> assertThat(className).contains("BigDecimalTo"))
+				.noneSatisfy((className) -> assertThat(className).contains("BigIntegerTo")));
 	}
 
 	@Test
diff --git a/module/spring-boot-mongodb/src/main/java/org/springframework/boot/mongodb/autoconfigure/MongoProperties.java b/module/spring-boot-mongodb/src/main/java/org/springframework/boot/mongodb/autoconfigure/MongoProperties.java
index f8491ae1ddc..78447bb640d 100644
--- a/module/spring-boot-mongodb/src/main/java/org/springframework/boot/mongodb/autoconfigure/MongoProperties.java
+++ b/module/spring-boot-mongodb/src/main/java/org/springframework/boot/mongodb/autoconfigure/MongoProperties.java
@@ -212,7 +212,7 @@ public class MongoProperties {
 		/**
 		 * Representation to use when converting a UUID to a BSON binary value.
 		 */
-		private UuidRepresentation uuid = UuidRepresentation.STANDARD;
+		private UuidRepresentation uuid = UuidRepresentation.UNSPECIFIED;
 
 		public UuidRepresentation getUuid() {
 			return this.uuid;