The present disclosure relates to a signal processing apparatus and method, an imaging element, and an electronic apparatus capable of suppressing deterioration of subjective image quality. Driving of a shift register controlling transfer of pixel data of digital data obtained by A/D conversion is stopped in a part or the entirety of a period in which the A/D conversion is performed on a pixel output of an analog signal. The present disclosure can be applied to, for example, a signal processing apparatus, an imaging element, an imaging device, an image processing apparatus, an electronic apparatus, a signal processing method, a program, or the like.