We consider a computational model for complex-fluid-solid interaction (CSFI) based on a diffuse-interface model for the complex fluid and a hyperelastic-material model for the solid. The diffuse-interface complex-fluid model is described by the incompressible Navier-Stokes-Cahn-Hilliard (NSCH) equations with preferential-wetting boundary conditions at the fluid-solid interface. The corresponding fluid traction on the interface includes a capillary-stress contribution,and the dynamic interface condition comprises the traction exerted by the non-uniform fluid-solid surface tension. We present a weak formulation of the aggregated CSFI problem,based on an arbitrary-Lagrangian-Eulerian formulation of the NSCH equations and a proper reformulation of the complex-fluid traction and the fluid-solid surface tension. To validate the presented CSFI model,we present numerical results and conduct a comparison to experimental data for a droplet on a soft substrate.