diff --git a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatOptions.java b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatOptions.java
index 831aedf227d..6c3e1246ca2 100644
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatOptions.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/OpenAiChatOptions.java
@@ -182,6 +182,15 @@ public class OpenAiChatOptions implements FunctionCallingOptions {
 	 * Developer-defined tags and values used for filtering completions in the <a href="https://platform.openai.com/chat-completions">dashboard</a>.
 	 */
 	private @JsonProperty("metadata") Map<String, String> metadata;
+
+	/**
+	 * Constrains effort on reasoning for reasoning models. Currently supported values are low, medium, and high.
+	 * Reducing reasoning effort can result in faster responses and fewer tokens used on reasoning in a response.
+	 * Optional. Defaults to medium.
+	 * Only for 'o1' models.
+	 */
+	private @JsonProperty("reasoning_effort") String reasoningEffort;
+
 	/**
 	 * OpenAI Tool Function Callbacks to register with the ChatModel.
 	 * For Prompt Options the functionCallbacks are automatically enabled for the duration of the prompt execution.
@@ -256,6 +265,7 @@ public static OpenAiChatOptions fromOptions(OpenAiChatOptions fromOptions) {
 			.toolContext(fromOptions.getToolContext())
 			.store(fromOptions.getStore())
 			.metadata(fromOptions.getMetadata())
+			.reasoningEffort(fromOptions.getReasoningEffort())
 			.build();
 	}
 
@@ -520,6 +530,14 @@ public void setMetadata(Map<String, String> metadata) {
 		this.metadata = metadata;
 	}
 
+	public String getReasoningEffort() {
+		return this.reasoningEffort;
+	}
+
+	public void setReasoningEffort(String reasoningEffort) {
+		this.reasoningEffort = reasoningEffort;
+	}
+
 	@Override
 	public OpenAiChatOptions copy() {
 		return OpenAiChatOptions.fromOptions(this);
@@ -532,7 +550,7 @@ public int hashCode() {
 				this.streamOptions, this.seed, this.stop, this.temperature, this.topP, this.tools, this.toolChoice,
 				this.user, this.parallelToolCalls, this.functionCallbacks, this.functions, this.httpHeaders,
 				this.proxyToolCalls, this.toolContext, this.outputModalities, this.outputAudio, this.store,
-				this.metadata);
+				this.metadata, this.reasoningEffort);
 	}
 
 	@Override
@@ -563,7 +581,8 @@ public boolean equals(Object o) {
 				&& Objects.equals(this.proxyToolCalls, other.proxyToolCalls)
 				&& Objects.equals(this.outputModalities, other.outputModalities)
 				&& Objects.equals(this.outputAudio, other.outputAudio) && Objects.equals(this.store, other.store)
-				&& Objects.equals(this.metadata, other.metadata);
+				&& Objects.equals(this.metadata, other.metadata)
+				&& Objects.equals(this.reasoningEffort, other.reasoningEffort);
 	}
 
 	@Override
@@ -740,6 +759,11 @@ public Builder metadata(Map<String, String> metadata) {
 			return this;
 		}
 
+		public Builder reasoningEffort(String reasoningEffort) {
+			this.options.reasoningEffort = reasoningEffort;
+			return this;
+		}
+
 		public OpenAiChatOptions build() {
 			return this.options;
 		}
diff --git a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
index a29ebcd8fcd..f73dc7b7d88 100644
--- a/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
+++ b/models/spring-ai-openai/src/main/java/org/springframework/ai/openai/api/OpenAiApi.java
@@ -58,6 +58,7 @@
  * @author Mariusz Bernacki
  * @author Thomas Vitale
  * @author David Frizelle
+ * @author Alexandros Pappas
  */
 public class OpenAiApi {
 
@@ -826,7 +827,8 @@ public record ChatCompletionRequest(// @formatter:off
 			@JsonProperty("tools") List<FunctionTool> tools,
 			@JsonProperty("tool_choice") Object toolChoice,
 			@JsonProperty("parallel_tool_calls") Boolean parallelToolCalls,
-			@JsonProperty("user") String user) {
+			@JsonProperty("user") String user,
+			@JsonProperty("reasoning_effort") String reasoningEffort) {
 
 		/**
 		 * Shortcut constructor for a chat completion request with the given messages, model and temperature.
@@ -838,7 +840,7 @@ public record ChatCompletionRequest(// @formatter:off
 		public ChatCompletionRequest(List<ChatCompletionMessage> messages, String model, Double temperature) {
 			this(messages, model, null, null, null, null, null, null, null, null, null, null, null, null, null,
 					null, null, null, false, null, temperature, null,
-					null, null, null, null);
+					null, null, null, null, null);
 		}
 
 		/**
@@ -852,7 +854,7 @@ public ChatCompletionRequest(List<ChatCompletionMessage> messages, String model,
 			this(messages, model, null, null, null, null, null, null,
 					null, null, null, List.of(OutputModality.AUDIO, OutputModality.TEXT), audio, null, null,
 					null, null, null, stream, null, null, null,
-					null, null, null, null);
+					null, null, null, null, null);
 		}
 
 		/**
@@ -867,7 +869,7 @@ public ChatCompletionRequest(List<ChatCompletionMessage> messages, String model,
 		public ChatCompletionRequest(List<ChatCompletionMessage> messages, String model, Double temperature, boolean stream) {
 			this(messages, model, null, null, null, null, null, null, null, null, null,
 					null, null, null, null, null, null, null, stream, null, temperature, null,
-					null, null, null, null);
+					null, null, null, null, null);
 		}
 
 		/**
@@ -883,7 +885,7 @@ public ChatCompletionRequest(List<ChatCompletionMessage> messages, String model,
 				List<FunctionTool> tools, Object toolChoice) {
 			this(messages, model, null, null, null, null, null, null, null, null, null,
 					null, null, null, null, null, null, null, false, null, 0.8, null,
-					tools, toolChoice, null, null);
+					tools, toolChoice, null, null, null);
 		}
 
 		/**
@@ -896,7 +898,7 @@ public ChatCompletionRequest(List<ChatCompletionMessage> messages, String model,
 		public ChatCompletionRequest(List<ChatCompletionMessage> messages, Boolean stream) {
 			this(messages, null, null, null, null, null, null, null, null, null, null,
 					null, null, null, null, null, null, null, stream, null, null, null,
-					null, null, null, null);
+					null, null, null, null, null);
 		}
 
 		/**
@@ -909,7 +911,7 @@ public ChatCompletionRequest streamOptions(StreamOptions streamOptions) {
 			return new ChatCompletionRequest(this.messages, this.model, this.store, this.metadata, this.frequencyPenalty, this.logitBias, this.logprobs,
 			this.topLogprobs, this.maxTokens, this.maxCompletionTokens, this.n, this.outputModalities, this.audioParameters, this.presencePenalty,
 			this.responseFormat, this.seed, this.serviceTier, this.stop, this.stream, streamOptions, this.temperature, this.topP,
-			this.tools, this.toolChoice, this.parallelToolCalls, this.user);
+			this.tools, this.toolChoice, this.parallelToolCalls, this.user, this.reasoningEffort);
 		}
 
 		/**
diff --git a/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiApiIT.java b/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiApiIT.java
index a3c098f6688..8c84fd98886 100644
--- a/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiApiIT.java
+++ b/models/spring-ai-openai/src/test/java/org/springframework/ai/openai/api/OpenAiApiIT.java
@@ -40,6 +40,7 @@
 /**
  * @author Christian Tzolov
  * @author Thomas Vitale
+ * @author Alexandros Pappas
  */
 @EnabledIfEnvironmentVariable(named = "OPENAI_API_KEY", matches = ".+")
 public class OpenAiApiIT {
@@ -66,6 +67,25 @@ void chatCompletionStream() {
 		assertThat(response.collectList().block()).isNotNull();
 	}
 
+	@Test
+	void validateReasoningTokens() {
+		ChatCompletionMessage userMessage = new ChatCompletionMessage(
+				"If a train travels 100 miles in 2 hours, what is its average speed?", ChatCompletionMessage.Role.USER);
+		ChatCompletionRequest request = new ChatCompletionRequest(List.of(userMessage), "o1", null, null, null, null,
+				null, null, null, null, null, null, null, null, null, null, null, null, false, null, null, null, null,
+				null, null, null, "low");
+		ResponseEntity<ChatCompletion> response = this.openAiApi.chatCompletionEntity(request);
+
+		assertThat(response).isNotNull();
+		assertThat(response.getBody()).isNotNull();
+
+		OpenAiApi.Usage.CompletionTokenDetails completionTokenDetails = response.getBody()
+			.usage()
+			.completionTokenDetails();
+		assertThat(completionTokenDetails).isNotNull();
+		assertThat(completionTokenDetails.reasoningTokens()).isPositive();
+	}
+
 	@Test
 	void embeddings() {
 		ResponseEntity<EmbeddingList<Embedding>> response = this.openAiApi