<p>Endwall film-cooling effectiveness experiments were conducted on a turbine guide vane using pressure sensitive paint measurement technique. Four film hole geometries, i.e., a fan-shaped hole, a horizontal slot hole, and two vertical slot holes with different expansion angles, were tested under a film hole layout that considered the actual multi-chamber construction. A continuous slot was set upstream of the endwall film holes to examine the influence of the upstream cooling. The experiments were performed at a mainstream Reynolds number of 620 000, a mainstream turbulence intensity of 3.7%, and a coolant-to-mainstream density ratio of 1.5. The results showed that the vertical slot holes perform better in the various chamber zones on the endwall than other hole geometries, in particular the zone with highly accelerated mainstream and the zone with large orientation angle. The vertical slot hole with a large exit expansion angle always yields the highest effectiveness on the endwall. The upstream slot cooling remarkably improves the endwall effectiveness and the influences are almost consistent for various hole geometries. Compared with the baseline fan-shaped hole, from blowing ratios of 1.0 to 2.5, the increase in the area-averaged effectiveness by large expansion angle vertical slot hole reaches 10.7%–39.1% without upstream slot cooling, while with upstream slot cooling, the increase decreases to 4.9%–23.1%. The discharge coefficient of various hole geometries on the endwall has almost no difference at small blowing ratios, and the difference at medium and high blowing ratios is also not great.</p>