A method for adjusting and testing an image sensor module is provided. The method of the present invention includes steps of: (1) calculating longitudinal and transverse deviation values of a center point of a lens relative to a standard reference position specified on a lens barrel, and an angle deviation value of the lens according to position signals of the lens on the image sensor module; (2) compensating the longitudinal and transverse deviation values of the center point of the lens, and the angle deviation value of the lens for exactly positioning the lens; and (3) adjusting focus of the image sensor module. The method of the present invention can compensate the mechanism errors produced in the mounting process of the image sensor module for conveniently and exactly adjusting the focus of the image sensor module. An apparatus for adjusting and testing an image sensor module is also provided.