diff --git a/src/__tests__/fields/array-field.spec.ts b/src/__tests__/fields/array-field.spec.ts
index 254fd7c..c49418a 100644
--- a/src/__tests__/fields/array-field.spec.ts
+++ b/src/__tests__/fields/array-field.spec.ts
@@ -139,4 +139,123 @@ describe("array-field", () => {
 			schema.validate({ items: [{ type: "other", description: "Custom type" }, { type: "A" }] })
 		).resolves.toBeDefined();
 	});
+
+	describe("unique validation", () => {
+		it("should validate unique field values across array items", () => {
+			const schema = jsonToSchema({
+				section: {
+					uiType: "section",
+					children: {
+						fruits: {
+							referenceKey: "array-field",
+							fieldSchema: {
+								name: {
+									uiType: "text-field",
+								},
+							},
+							validation: [
+								{
+									unique: [{ field: "name", errorMessage: ERROR_MESSAGE }],
+									errorMessage: ERROR_MESSAGE,
+								},
+							],
+						},
+					},
+				},
+			});
+
+			// Valid - all unique values
+			expect(() =>
+				schema.validateSync({
+					fruits: [{ name: "Apple" }, { name: "Banana" }],
+				})
+			).not.toThrowError();
+
+			// Invalid - duplicate name
+			expect(
+				TestHelper.getError(() =>
+					schema.validateSync({
+						fruits: [{ name: "Apple" }, { name: "Apple" }],
+					})
+				).message
+			).toBe(ERROR_MESSAGE);
+		});
+
+		it("should validate multiple unique fields", () => {
+			const schema = jsonToSchema({
+				section: {
+					uiType: "section",
+					children: {
+						fruits: {
+							referenceKey: "array-field",
+							fieldSchema: {
+								name: {
+									uiType: "text-field",
+								},
+								colour: {
+									uiType: "text-field",
+								},
+							},
+							validation: [
+								{
+									unique: [{ field: "name" }, { field: "colour" }],
+								},
+							],
+						},
+					},
+				},
+			});
+
+			// Valid - all unique values
+			expect(() =>
+				schema.validateSync({
+					fruits: [
+						{ name: "Apple", colour: "Red" },
+						{ name: "Banana", colour: "Yellow" },
+					],
+				})
+			).not.toThrowError();
+
+			// Invalid - duplicate colour
+			expect(() =>
+				schema.validateSync({
+					fruits: [
+						{ name: "Apple", colour: "Red" },
+						{ name: "Cherry", colour: "Red" },
+					],
+				})
+			).toThrowError();
+		});
+
+		it("should use default error message when errorMessage is not provided", () => {
+			const schema = jsonToSchema({
+				section: {
+					uiType: "section",
+					children: {
+						fruits: {
+							referenceKey: "array-field",
+							fieldSchema: {
+								name: {
+									uiType: "text-field",
+								},
+							},
+							validation: [
+								{
+									unique: [{ field: "name" }],
+								},
+							],
+						},
+					},
+				},
+			});
+
+			expect(
+				TestHelper.getError(() =>
+					schema.validateSync({
+						fruits: [{ name: "Apple" }, { name: "Apple" }],
+					})
+				).message
+			).toBe("One or more fields are not unique");
+		});
+	});
 });
diff --git a/src/fields/array-field.ts b/src/fields/array-field.ts
index 6749875..68beaa3 100644
--- a/src/fields/array-field.ts
+++ b/src/fields/array-field.ts
@@ -4,33 +4,77 @@ import { ICustomFieldSchemaBase, IValidationRule, TComponentSchema, jsonToSchema
 import { ERROR_MESSAGES } from "../shared";
 import { IFieldGenerator } from "./types";
 
+export interface IArrayFieldUniqueRule {
+	field: string;
+	errorMessage?: string | undefined;
+}
+
 interface IArrayFieldValidationRule extends IValidationRule {
 	/** for customising error message when one section is invalid */
 	valid?: boolean | undefined;
+	/** Specify child fields that must be unique across all array items, with a custom error message per field. */
+	unique?: IArrayFieldUniqueRule[] | undefined;
 }
 
-export interface IArrayFieldSchema<V = undefined>
-	extends ICustomFieldSchemaBase<"array-field", V, IArrayFieldValidationRule> {
+export interface IArrayFieldSchema<V = undefined> extends ICustomFieldSchemaBase<
+	"array-field",
+	V,
+	IArrayFieldValidationRule
+> {
 	fieldSchema: Record<string, TComponentSchema>;
 }
 
 export const arrayField: IFieldGenerator<IArrayFieldSchema> = (id, { fieldSchema, validation }) => {
 	const isRequiredRule = validation?.find((rule) => "required" in rule);
+	const uniqueRule = validation?.find((rule) => "unique" in rule) as IArrayFieldValidationRule | undefined;
 
 	// Create fresh schema instance per array item to prevent mutation conflicts during parallel async validation
 	const itemSchema = Yup.lazy(() => jsonToSchema({ section: { uiType: "section", children: fieldSchema } }));
 
+	let yupSchema = Yup.array(itemSchema).test(
+		"is-empty-array",
+		isRequiredRule?.errorMessage || ERROR_MESSAGES.ARRAY_FIELD.REQUIRED,
+		(value) => {
+			if (!value || !isRequiredRule?.required) return true;
+
+			return value.length > 0 && value.some((item) => !isEmpty(item));
+		}
+	);
+
+	if (uniqueRule?.unique?.length) {
+		yupSchema = yupSchema.test(
+			"unique-items",
+			uniqueRule?.errorMessage || ERROR_MESSAGES.ARRAY_FIELD.UNIQUE,
+			(value) => {
+				if (!value) return true;
+
+				const errors: Record<string, string>[] = [];
+				let hasError = false;
+
+				uniqueRule.unique.forEach(({ field, errorMessage }) => {
+					const fieldValues = value.map((item) => item?.[field]);
+
+					fieldValues.forEach((val, idx) => {
+						if (!val) return;
+						const isDuplicate = fieldValues.findIndex((v) => v === val) !== idx;
+						if (isDuplicate) {
+							errors[idx] = {
+								...errors[idx],
+								[field]: errorMessage || ERROR_MESSAGES.ARRAY_FIELD.UNIQUE,
+							};
+							hasError = true;
+						}
+					});
+				});
+
+				return !hasError;
+			}
+		);
+	}
+
 	return {
 		[id]: {
-			yupSchema: Yup.array(itemSchema).test(
-				"is-empty-array",
-				isRequiredRule?.errorMessage || ERROR_MESSAGES.ARRAY_FIELD.REQUIRED,
-				(value) => {
-					if (!value || !isRequiredRule?.required) return true;
-
-					return value.length > 0 && value.some((item) => !isEmpty(item));
-				}
-			),
+			yupSchema,
 			validation,
 		},
 	};
diff --git a/src/shared/error-messages.ts b/src/shared/error-messages.ts
index 35d21ae..26d2151 100644
--- a/src/shared/error-messages.ts
+++ b/src/shared/error-messages.ts
@@ -86,5 +86,6 @@ export const ERROR_MESSAGES = {
 	ARRAY_FIELD: {
 		INVALID: "One or more of the sections is incomplete",
 		REQUIRED: "At least one section must be filled in",
+		UNIQUE: "One or more fields are not unique",
 	},
 };