We demonstrate multiple photon cycling and radiative force deflection on the triatomic free radical strontium monohydroxide (SrOH). Optical cycling is achieved on SrOH in a cryogenic buffer-gas beam by employing the rotationally closed P ( N ″ = 1 ) branch of the vibronic transition X ˜ 2 Σ + ( 000 ) ↔ A ˜ 2 Π 1 / 2 ( 000 ) . A single repumping laser excites the Sr–O stretching vibrational mode, and photon cycling of the molecule deflects the SrOH beam by an angle of 0.2 ° via scattering of ∼100 photons per molecule. This approach can be used for direct laser cooling of SrOH and more complex, isoelectronic species.