The ubiquitous presence and increasing concentrations of microplastics (¡ 5 mm in size), particularly in aquaculture facilities, raise concerns regarding its interaction with farmed organisms and potential contamination of human food supply. Adverse physiological and metabolic responses from microplastic ingestion in aquatic organisms have mostly been addressed under laboratory conditions after exposure to very high levels. Moreover, little is known considering farmed species. This study aimed at evaluating the short-term sub-lethal effects on the oxidative stress status, neurotoxicity and metabolic level of meagre fish larvae Argyrosomus regius (15 days post-hatching), caused by 3 h of exposure to polyethylene microplastics (PEMPs; tested concentrations: 0.1, 1 and 10 mg/L; n=16, in the presence or absence of food (alive Artemia nauplii, 5 org/mL). After 3 h exposure, fish larvae presented PEMPs in the gut: 1 ± 0.2 to 1.1 ± 0.2 and ¡ 1 to 1.3 ± 0.4 particles/larvae in the absence and presence of food, respectively. In the absence of food, PEMP ingestion: (1) affected the antioxidant defences of meagre fish larvae through a generalised inhibition of the catalase activity, decrease in glutathione-S-transferases, and an increase of total glutathione in the medium and highest tested concentrations; without, however, cause oxidative damage (LPO); (2) inhibited acetylcholinesterase activity; (3) incremented the aerobic energy production. Such biochemical effects were similar in the presence of food, except for the aerobic energy production, which increased significantly in the lowest and medium tested PEMP concentrations. Although a short exposure to PEMPs in relevant aquaculture scenarios (presence of food) seems not to compromise fish larvae homeostasis, it cannot rule out potential adverse effects under a chronic exposure – with potential alterations on fish development, nutritional value and fitness.