The invention provides a class of photochromic polydiorganosiloxane vinylic crosslinkers. Each of the photochromic polydiorganosiloxane vinylic crosslinkers of the invention comprise (1) a polydiorganosiloxane polymer chain comprising dimethylsiloxane units and photochromic siloxane unit having one methyl substituent and one organic substituent having a photochromic moiety that capable of undergoing a reversible color change upon exposure to UV-irradiation or high-energy-violet light; (2) two terminal ethylenically-unsaturated groups. The invention also provides a soft photochromic contact lens, especially a photochromic silicone hydrogel contact lens, which comprises a crosslinked polymeric material comprising repeating units of at least one of such a class of photochromic polydiorganosiloxane vinylic crosslinkers. The invention further provides a method of producing a photochromic contact lens from a polymerizable composition comprising at least one of such a class of photochromic polydiorganosiloxane vinylic crosslinkers.