Nowadays seabirds are among the most threatened animal taxa. Due to introduction by humans of mammalian predators on large islands, Mediterranean Storm Petrels are now confined to islets and considered locally vulnerable, especially threatened by predatory overabundant gulls. In this study, we evaluate the effectiveness of nest boxes installation as a management measure for their conservation at Benidorm Island (Spain). We compare demographic parameters of individuals breeding in natural nests and nest boxes using capture–recapture and generalized linear mixed models. Our results show higher survival rates and breeding success probabilities for birds breeding in artificial nests than in natural sites, probably as a consequence of protection against gulls. Following the installation and successful occupation of nest boxes, breeding numbers of Storm Petrels greatly increased. Although conservation measures have proved highly effective we recommend the maintenance of the monitoring and evidence-based management of the Storm Petrel breeding population.