Solar absorber Cu2ZnSnS4 (CZTS) films were uniformly deposited on Si/Mo substrates via a facile, cost-effective chemical bath deposition (CBD) by using ribonucleic acid (RNA) nucleobase uracil as the functional building block. The functional sites of uracil, i.e., C=O and N-H, played a critical role in the complexation of metals via uracil-quartet functional architectures. Stable metal-uracil complexes significantly affected the growth kinetics, enhancing the uniform delivery of multimetal components into films and suppressing the undesirable formation of CuS particles. CZTS films obtained with the addition of 0.05 and 0.5 M uracil exhibited a smooth surface morphology and significantly improved photoconductive performance. The developed RNA-nucleobase-mediated CBD method demonstrates promise as multicomponent compound absorber films, including CZTS and CuInGaSe2, in cost-effective solar cells.