A three-dimensional (3D) image capture method, employed in an electronic device with a monocular camera and a 3D display, includes at least the following steps: while the electronic device is moving, deriving a 3D preview image from a first preview image and a second preview image generated by the monocular camera, and providing 3D preview on the 3D display according to the 3D preview image, wherein at least one of the first preview image and the second preview image is generated while the electronic device is moving; and when a capture event is triggered, outputting the 3D preview image as a 3D captured image.