This paper presents a time-of-flight (ToF) CMOS image sensor with pulse-frequency-modulation (PFM) pixel for in-pixel code discrimination (CD). One of ToF’s main problem is interference between multiple sensors or malicious one by third pirty. CD is a function that discriminates signal light from the others with code modulation, which will be an effective countermeasure against such interference. Proposed pixel contains a PFM circuit and counters, with which in-pixel CD and distance measurement (DM) is tried to be realized. In this paper, method of CD and DM, circuit implementation, and simulation results of the system operation on C programs are shown.