Tremendous attention has been paid to vertically stacked heterostructures owing to their tunable electronic structures and outstanding optical properties. In this work, we explore the structural, electronic and optical properties of vertically stacked GaN/WX₂ (X = S, Se, Te) heterostructures using density functional theory. We find that these stacking heterostructures are all semiconductors with direct band gaps of 1.473 eV (GaN/WTe₂), 2.102 eV (GaN/WSe₂) and 1.993 eV (GaN/WS₂). Interestingly, the GaN/WS₂ heterostructure exhibits a type-II band alignment, while the other two stackings of GaN/WSe₂ and GaN/WTe₂ heterostructures have type-I band alignment. The optical absorption of GaN/WX₂ heterostructures is very efficient in the visible light spectrum. Our results suggest that GaN/WX₂ heterostructures are promising candidates for photocatalytic water splitting and photoelectronic devices in visible light.