The severity of Botrytis cinerea growth could be significantly inhibited in mature strawberry fruits by priming fungal resistance in harvested berries after the proactive application of UV-B light (312 nm). Harvested fruits were irradiated by accumulative UV-B light amounts (0, 0.33, 0.65, and 1.3 mJoule/cm2) before being artificially infected with B. cinerea. PCR assay could estimate a reduction ratio of 50 % in fungal DNA in fruits proactively exposed to UV-B light (1.3 mJoule/cm2). These fruits showed a minimum fungal severity level compared to non-UV-B treated fruits (0 mJoule/cm2), which were harshly rotted with velvety gray mold growth. To reveal a side of possible molecular mechanisms behind UV-B induced immunity in ripe berries against B. cinerea, the expression profiles of some resistance-related genes were quantified using real-time PCR on day 1 and day 2 after infection. UV-B significantly sharpens the expression of strawberry defense gene FaBG2-1 which encodes the fungal cell wall degrading enzyme β-1-3-glucanase. Furthermore, jasmonic acid (JA) biosynthesis key gene FaAOS was strongly up-regulated after exposure to UV-B in infected or non-infected fruits on day 2. Equally important, the expression of FaNES1, volatile terpenoids linalool/nerolidol synthase gene, was moderately elevated. ABA signaling gene FaPYR1 was found to be more responsive on day 2 after UV-B irradiation. Collectively, we hypothesize that UV-B proactive irradiation can encourage the enhancement of the molecular immune system in mature strawberry fruits against possible B. cinerea infection postharvest. Further studies are needed to reveal UV-B potential as a sustainable priming agent against plant diseases.