This paper presents the findings of an experimental and numerical investigation on the shock effect on heat transfer coefficient and film-cooling effectiveness. In this study, coolant was injected on the blade surface through a fan-shaped hole in a transonic cascade. The experimental results indicate that on the film-cooled suction surface of the blade, the shock from the adjacent blade impinging on the suction surface causes the film-cooling effectiveness to drop quickly by 18%, and then stay at a low level downstream of the shock. The shock also causes the local heat transfer coefficient to decrease rapidly by 25%, but then rise back up immediately after the shock. The results from the numerical study supported the film-cooling effectiveness and heat transfer coefficient trends that were observed in the experiment. A detailed analysis of the numerical results reveals that the rapid change of the film-cooling effectiveness is due to the near surface secondary flows, which push the hot mainstream air toward the injection centerline and lifts the low temperature core away from the surface. This secondary flow is a result of a spanwise pressure gradient. The drop in heat transfer coefficient is caused by a boundary layer separation bubble which results from an adverse streamwise pressure gradient at the shock position.