RuII–bis‐pyridine complexes typically absorb below 450 nm in the UV spectrum and their molar extinction coefficients are only moderate (ε<16 000 M−1 cm−1). Thus, RuII–polyimine complexes that show intense visible‐light absorptions are of great interest. However, no effective light‐harvesting ruthenium(II)/organic chromophore arrays have been reported. Herein, we report the first visible‐light‐harvesting RuII–coumarin arrays, which absorb at 475 nm (ε up to 63 300 M−1 cm−1, 4‐fold higher than typical RuII–polyimine complexes). The donor excited state in these arrays is efficiently converted into an acceptor excited state (i.e., efficient energy‐transfer) without losses in the phosphorescence quantum yield of the acceptor. Based on steady‐state and time‐resolved spectroscopy and DFT calculations, we proposed a general rule for the design of RuII–polypyridine–chromophore light‐harvesting arrays, which states that the 1IL energy level of the ligand must be close to the respective energy level of the metal‐to‐ligand charge‐transfer (MLCT) states. Lower energy levels of 1IL/3IL than the corresponding 1MLCT/3MLCT states frustrate the cascade energy‐transfer process and, as a result, the harvested light energy cannot be efficiently transferred to the acceptor. We have also demonstrated that the light‐harvesting effect can be used to improve the upconversion quantum yield to 15.2 % (with 9,10‐diphenylanthracene as a triplet‐acceptor/annihilator), compared to the parent complex without the coumarin subunit, which showed an upconversion quantum yield of only 0.95 %.