Freshwater ecosystems are increasingly exposed to pharmaceutical contamination, impacting non-target species. Concentrations can vary over time and location, allowing for potential acclimation or recovery effects. Additionally, parasites might interfere with the absorption and adverse outcomes pathways of pollutants. We examined the combined effects of paracetamol and parasite on the behavior and coloration of the European chub (Squalius cephalus), a ubiquitous fish species, from natural populations. Fish were exposed in mesocosms to acute doses of paracetamol (16 μg g