Plastics are emerging drivers of environmental change that may influence marine near-shore ecosystems. Polystyrene (PS) is among the most produced polymers worldwide and is frequently found in the marine environment. Under environmental conditions, PS plastics brittle and break down into smaller particles, becoming more available to biota. Although various studies have been focusing on the effects of microplastics, information concerning the impacts of these contaminants on anemones is scarce. Anemones are among the most abundant groups of animals found in rocky shore habitats, maintaining equilibrium by providing habitat, food and protection for other species. Hence, this study aimed to assess the effects of PS microplastics on behavior (reaction time to touch (RT): mouth tightness aftertouch (MT), and mouth reopening after being closed (MR)) of the anemones Actinia equina and Aulactinia verrucosa. Percentage of nonresponsive anemones (NR) and exported water content after being exposed to air (WCE) was also assessed. The anemones Actinia equina and Aulactinia verrucosa were collected in a rocky shore - Praia da Granja (Portugal), and after depuration and acclimation were exposed for seven days to 3 µm PS microplastics particles (0.0; 0.001; 0.01; 0.1: 1.0; 10 mg/L). Results demonstrated that PS microplastics impacted the behavior of A. equina and A. verrucosa. MT and RT in A. equina decreased in exposed organisms (except at 0.01mg/L for MT and 10 mg/L for RT). MR increased at high concentrations (10 mg/L). The NR was higher in exposed organisms, with a peak at 0.01 mg/L. Concerning A. verrucosa, RT, MR and NR increased with concentration increase; MT increased in lower concentrations (0.1; 0.01 and 0.001 mg/L). WCE increased with the concentration increase for both species. Overall, results demonstrated that PS microplastics may present potential impacts for the studied species and, consequently, put at risk these populations.