External deposition on a slot film cooled nozzle guide vane, subjected to nonuniform inlet temperatures, was investigated experimentally and computationally. Experiments were conducted using a four-vane cascade, operating at temperatures up to 1353 K and inlet Mach number of approximately 0.1. Surveys of temperature at the inlet and exit planes were acquired to characterize the form and migration of the hot streak. Film cooling was achieved on one of the vanes using a single spanwise slot. Deposition was produced by injecting sub-bituminous ash particles with a median diameter of 6.48 μm upstream of the vane passage. Several deposition tests were conducted, including a baseline case, a hot streak-only case, and a hot streak and film cooled case. Results indicate that capture efficiency is strongly related to both the inlet temperature profiles and film cooling. Deposit distribution patterns are also affected by changes in vane surface temperatures. A computational model was developed to simulate the external and internal flow, conjugate heat transfer, and deposition. Temperature profiles measured experimentally at the inlet were applied as thermal boundary conditions to the simulation. For deposition modeling, an Eulerian–Lagrangian particle tracking model was utilized to track the ash particles through the flow. An experimentally tuned version of the critical viscosity sticking model was implemented, with predicted deposition rates matching experimental results well. Comparing overall deposition rates to results from previous studies indicates that the combined effect of nonuniform inlet temperatures and film cooling cannot be accurately simulated by simple superposition of the two independent effects; thus, inclusion of both conditions in experiments is necessary for realistic simulation of external deposition.