A coupled kinetic-fluid model is investigated, which describes the dynamic behavior of an ensemble of Cucker–Smale flocking particles interacting with a viscous fluid in a three-dimensional bounded domain. This system consists of a kinetic Cucker–Smale equation and a compressible Navier–Stokes system with nonhomogeneous boundary conditions. The global existence of weak solutions to this system with adiabatic coefficient γ>3/2 is established.