Expanding the catalytic environment to a nanosize must be one of the most promising ways to improve the performance of homogeneous catalysts. In this Forum Article, recent developments in homogeneous nanosize palladium catalysts are reviewed. It contains solubilized palladium nanoparticles, metalated dendrimers, and complexes with well-defined nanosized ligands. These systems realize efficient catalyst recycling, unique selectivity, suppression of metal aggregation, and remarkable enhancement of the catalytic activity.