Tin (Sn)‐based perovskites with favorable optoelectronic properties and ideal bandgaps have emerged as promising alternatives to toxic lead (Pb)‐based perovskites for photovoltaic applications. However, it is challenging to obtain high‐quality Sn‐based perovskite films by solution process. Here, liquid‐exfoliated 2D transition‐metal dichalcogenides (i.e., MoS₂, WS₂, and WSe₂) with smooth and defect‐free surfaces are applied as growth templates for spin‐coated FASnI₃ perovskite films, leading to van der Waals epitaxial growth of perovskite grains with a growth orientation along (100). The authors find that WSe₂ has better energy alignment with FASnI₃ than MoS₂ and WS₂ and results in a cascade band structure in resultant perovskite solar cells (PSCs), which can facilitate hole extraction and suppress interfacial charge recombination in the devices. The WSe₂‐modified PSCs show a power conversion efficiency up to 10.47%, which is among the highest efficiency of FASnI₃‐based PSCs. The appealing solution phase epitaxial growth of FASnI₃ perovskite on 2D WSe₂ flakes is expected to find broad applications in optoelectronic devices.