The use of hybrids is widespread in agriculture yet the molecular basis for hybrid vigor (heterosis) remains obscure. To identify molecular components of the leaf that may contribute to the known higher photosynthetic capacity of maize hybrids, we generated paired datasets of the proteomes and transcriptomes from leaf tissues of maize hybrids and their inbred parents. Expression patterns in the hybrids were semi-dominant to overdominant for subunits of the digenomic protein complexes required for the light reactions of photosynthesis and for chloroplast protein synthesis; nuclear and plastid-encoded subunits were elevated similarly. These patterns were not mirrored in the nuclear transcriptomes. We compared growth of multiple hybrids with varying levels of heterosis to transcript and protein levels. Expression heterosis (hybrid/mid-parent expression levels) of chloroplast ribosomal proteins and of nuclear transcripts for the photosynthetic light reactions was positively correlated with plant height heterosis (hybrid/mid-parent plant height). Ethylene biosynthetic enzymes were expressed below mid-parent levels in the hybrids, and the ethylene biosynthesis mutant acs2/acs6 partially phenocopied the hybrid proteome, indicating that a reduction in ethylene biosynthesis may be upstream of the elevated expression of photosynthetic and ribosomal proteins in chloroplasts of hybrids.