Given their ability to fix atmospheric nitrogen, legumes are pivotal to the development of sustainable agriculture in Europe as a source of protein for food and feed. Pea (Pisum sativum) is currently the leading grain legume crop in France and major efforts are being made to reintroduce legumes as protein crops in Europe. However, instability of seed yield and quality due to environmental fluctuations still represent a real barrier for the development of these cultures, and breeding for stable yields is needed. In pea, drought stress occurring during the reproductive phase can greatly affect seed yield and quality. We investigated the response of pea plants (var. Caméor) subjected to water stress during the seed filling period, a phase associated with massive remobilization of nutrients from the vegetative organs (including leaves) to sustain the seed’s high-nitrogen demand. Transcriptomic profiling of leaf response to water stress by hybridization of a 40k pea micro-array revealed metabolic and regulatory pathways affected by drought and enabled the selection of candidate genes for drought resistance. One of these genes, named RAMOSUS1, encodes a carotenoid cleavage dioxygenase involved in strigolactone biosynthesis. Interestingly, phenotyping of the corresponding mutant showed it to have increased sensitivity to drought compared to the wild-type, suggesting that strigolactones could act as positive regulators for crop abiotic stress resistance, as already shown for Arabidopsis.