Isolated systems like islands, experience important problems related to microplastic debris on their beaches [1,2]. This problem is also increased by the formation of microbial biofilms on the surface of the microplastics present in such aquatic environments, which provides potential facilities for microorganisms to survive in the biofilm. Apart from that, microplastics act as a vehicle for the dispersion of pathogenic organisms around coastal waters, constituting a new route of exposure for humans [3]. Although in Europe, the Bathing Water Directive uses Faecal Indicator Organisms (FIO), such as Escherichia coli and Intestinal enterococci, as key parameters for the monitoring and control of bathing water quality (Directive 2000/7/EC), their presence is not analysed in microplastics deposited on such beaches, despite the fact that they provide a more durable substrate for these and other microorganisms than their natural reservoirs [4]. The objective of this study was to analyze the microbial content (FIO and Vibrio spp) of microplastics (fragments and pellets) collected on six beaches (Almáciga, El Socorro, Las Teresitas, Playa Grande, Puertito de Adeje, La Viuda and Punta del Bocinegro) on Tenerife, Canary Islands (Spain). Results show that Escherichia coli was present in 57.1% of the fragments and 28.5 % of the pellets studied. In the case of Intestinal enterococci, 85.7% of the fragments and 57.1% of the pellets tested positive for this parameter. Finally, 100% of the fragments and 42.8% of the pellets analyzed in the different beaches contained Vibrio spp. Results obtained in this study show that microplastics act as reservoirs of microorganisms that can increase the presence of bacteria that indicate faecal and pathogen contamination in bathing areas. 1 Mar. Pollut. Bull., 2019, 146, 26–32. 2 Mar. Pollut. Bull., 2020, 151, 110847. 3 Trends Microbiol., 2021, 29, 107–126. 4 Nat. Rev. Microbiol. 2020, 18, 139–151.