The occurrence of marine litter, mostly plastic items, is on a widespread constant increase. The ingestion of plastic by marine organisms depends on its availability in the environment and its physical properties. Zooplankton represents a crucial food source for many secondary consumers, thus, the relative abundance and similarities between plastic particles and planktonic organisms define the probability for these particles to enter the food web and transfer up the trophic levels. The temporal overlap between the consumers' occurrence, which mainly depends on the presence of the food source, and the debris accumulation also represents a critical factor. In this context, the present study describes the seasonal variation in the abundance, types and sizes of microplastics and zooplankton in a pelagic environment. Monthly samplings of surface waters were carried out off the South coast of Madeira Island (bathymetry ¿ 1000 m) during 2019. The plastic particles collected were counted and classified into different categories (fragment, line, film, foam, fibre) and size classes (