Litter are ubiquitous and increasing in the coastal and marine environments. Entanglement with litter is one of the principal causes of mortality in seabirds, but the population-level consequences are unknown. Currently, all seabirds collect litter for nesting material. Northern Gannets are not the exception and there are several cases where elevated percentages of polymers are part of the life cycle of gannets, especially during breeding. This baseline paper presents an analysis of litter content and its related impacts on the two gannet nests located in South France (Carry-Le-Rouet) and Northwest Italy (Portovenere) from 2017 to 2019. 654 items from both gannet nests were collected with 277 items (42%) being of natural origin, while 377 items (58%) were litter. Most of the nesting material was nautical cordage, which appears to be used preferentially. A more restrictive litter management regulation must be adopted to reduce litter generation from fishing/aquaculture-related activities. •Analysis of litter content of two Mediterranean gannet nests in France and Italy•Litter always was found in both nests, and its impact on the birds highlighted.•Portovenere was the most polluted in terms of litter percentage in the nest.•Four typologies of polymeric items accounted for 73% of all litter in both nests.•Restrictive management regulation to reduce litter from fishing/aquaculture