Hybrid organic−inorganic halide perovskites (HOIPs) with intrinsic noncentrosymmetry are an emerging class of semiconducting materials that has been revolutionizing the field of optoelectronics including second-order nonlinear optics (NLO). Following an upsurge in three-dimensional (3D) perovskites, more recently, low-dimensional perovskite materials have displayed desirable NLO responses attributed to structural diversity, strong quantum confinement, and remarkable exciton effect. Herein, using first-principles methods, we elucidate a linear photogalvanic effect (LPGE) photocurrent (shift photocurrent, SPC) with a maximum amplitude of ∼430 μAV −2 in a quasi-two-dimensional (2D) leadfree HOIP, (CH 3 ) 2 NH 2 SnI 3 (DMASnI 3 ). The simulated SPC whose prominent peaks occur predominantly in the ultraviolet (UV) range is about 8-fold larger in magnitude compared to its 3D counterpart. From the orbital characteristics of the initial and final states, the calculated SPC is attributed to the contributions from the electronic properties of Sn and I whose p-states control the band edges. The organic-cation orientation indirectly influences the bandgap size, valence and conduction band edge behavior, as well as the position of the Fermi level, slightly altering the LPGE photocurrent spectrum. The findings of this work demonstrate the quasi-2D organic tin triiodide perovskite as a promising lead-free alternative for NLO devices.