diff --git a/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequest.java b/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequest.java
index 8522af771c..ff40a30785 100644
--- a/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequest.java
+++ b/oauth2/oauth2-core/src/main/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequest.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -440,7 +440,21 @@ public final class OAuth2AuthorizationRequest implements Serializable {
 			Map<String, Object> parameters = getParameters(); // Not encoded
 			this.parametersConsumer.accept(parameters);
 			MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
-			parameters.forEach((k, v) -> queryParams.set(encodeQueryParam(k), encodeQueryParam(String.valueOf(v)))); // Encoded
+			parameters.forEach((k, v) -> {
+				String key = encodeQueryParam(k);
+				if (v instanceof Iterable) {
+					((Iterable<?>) v).forEach((value) -> queryParams.add(key, encodeQueryParam(String.valueOf(value))));
+				}
+				else if (v != null && v.getClass().isArray()) {
+					Object[] values = (Object[]) v;
+					for (Object value : values) {
+						queryParams.add(key, encodeQueryParam(String.valueOf(value)));
+					}
+				}
+				else {
+					queryParams.set(key, encodeQueryParam(String.valueOf(v)));
+				}
+			});
 			UriBuilder uriBuilder = this.uriBuilderFactory.uriString(this.authorizationUri).queryParams(queryParams);
 			return this.authorizationRequestUriFunction.apply(uriBuilder).toString();
 		}
diff --git a/oauth2/oauth2-core/src/test/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequestTests.java b/oauth2/oauth2-core/src/test/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequestTests.java
index 1a912d58a8..1c4365560d 100644
--- a/oauth2/oauth2-core/src/test/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequestTests.java
+++ b/oauth2/oauth2-core/src/test/java/org/springframework/security/oauth2/core/endpoint/OAuth2AuthorizationRequestTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2022 the original author or authors.
+ * Copyright 2002-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@ package org.springframework.security.oauth2.core.endpoint;
 import java.net.URI;
 import java.util.Arrays;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
@@ -319,4 +320,49 @@ public class OAuth2AuthorizationRequestTests {
 						+ "item%20amount=19.95%E2%82%AC&%C3%A2ge=4%C2%BD&item%20name=H%C3%85M%C3%96");
 	}
 
+	@Test
+	public void buildWhenAdditionalParametersContainsArrayThenProperlyEncoded() {
+		Map<String, Object> additionalParameters = new LinkedHashMap<>();
+		additionalParameters.put("item1", new String[] { "1", "2" });
+		additionalParameters.put("item2", "value2");
+		OAuth2AuthorizationRequest authorizationRequest = TestOAuth2AuthorizationRequests.request()
+			.additionalParameters(additionalParameters)
+			.build();
+		assertThat(authorizationRequest.getAuthorizationRequestUri()).isNotNull();
+		assertThat(authorizationRequest.getAuthorizationRequestUri())
+			.isEqualTo("https://example.com/login/oauth/authorize?response_type=code&client_id=client-id&state=state&"
+					+ "redirect_uri=https://example.com/authorize/oauth2/code/registration-id&"
+					+ "item1=1&item1=2&item2=value2");
+	}
+
+	@Test
+	public void buildWhenAdditionalParametersContainsIterableThenProperlyEncoded() {
+		Map<String, Object> additionalParameters = new LinkedHashMap<>();
+		additionalParameters.put("item1", Arrays.asList("1", "2"));
+		additionalParameters.put("item2", "value2");
+		OAuth2AuthorizationRequest authorizationRequest = TestOAuth2AuthorizationRequests.request()
+			.additionalParameters(additionalParameters)
+			.build();
+		assertThat(authorizationRequest.getAuthorizationRequestUri()).isNotNull();
+		assertThat(authorizationRequest.getAuthorizationRequestUri())
+			.isEqualTo("https://example.com/login/oauth/authorize?response_type=code&client_id=client-id&state=state&"
+					+ "redirect_uri=https://example.com/authorize/oauth2/code/registration-id&"
+					+ "item1=1&item1=2&item2=value2");
+	}
+
+	@Test
+	public void buildWhenAdditionalParametersContainsNullThenAuthorizationRequestUriContainsNull() {
+		Map<String, Object> additionalParameters = new LinkedHashMap<>();
+		additionalParameters.put("item1", null);
+		additionalParameters.put("item2", "value2");
+		OAuth2AuthorizationRequest authorizationRequest = TestOAuth2AuthorizationRequests.request()
+			.additionalParameters(additionalParameters)
+			.build();
+		assertThat(authorizationRequest.getAuthorizationRequestUri()).isNotNull();
+		assertThat(authorizationRequest.getAuthorizationRequestUri())
+			.isEqualTo("https://example.com/login/oauth/authorize?response_type=code&client_id=client-id&state=state&"
+					+ "redirect_uri=https://example.com/authorize/oauth2/code/registration-id&"
+					+ "item1=null&item2=value2");
+	}
+
 }