The synthesis of photocrosslinkable fluorinated polydimethylsiloxanes was achieved through direct hydrosilylation with copoly(dimethyl)(methyl-hydrogen) siloxane. First, the hydrosilylation of a fluorinated olefin allowed the introduction of a fluorinated group onto the polysiloxane. Then, a second hydrosilylation of allyl methyl methacrylate led to the polysiloxane bearing both fluorinated and photocrosslinkable groups. This method, compared with a previous method of copolycondensation, is shown to be easier and more efficient. All the new products synthesized were characterized by IR, H-1 NMR, F-19 NMR, and Si-29 NMR. A formulation containing the fluorosilicone was crosslinked after being coated on a mesoporous membrane and was evaluated as a vapor permeation membrane.