<p>The Atlantic blue crab <i>Callinectes sapidus</i> occurs as an invasive alien species in the Mediterranean, where it has successfully colonized the entire basin, exerting a negative impact on fisheries in some areas. This paper presents the results of a study on the movement ecology of blue crabs in the S’Ena Arrubia lagoon, a shallow, oligohaline, semi-enclosed water body used for extensive aquaculture in Sardinia (western Mediterranean). The specific objective was to investigate movements and home range of blue crabs in the lagoon and evaluate the effect of temperature on movement patterns. An array of 15 receivers was deployed in the lagoon. Two batches of adult blue crabs were tagged with external ultrasonic transmitters: a first lot (5 males and 5 females) was released in December 2022, and a second lot (10 females) in June 2023. Monitoring lasted 290 days for the first lot and 202 days for the second. Residency and movement index, daily home range (MCPd), and Vemco Positioning System (VPS) data were used to describe crab movements and activity patterns. Residency and movement indexes were larger than 80% for 16 and 8 crabs, respectively. MCPd values ranged between 2516.9 m² and 21207.2 m². The movement rate, used as a proxy of activity, was lower for males than for females in spring and summer. Females tended to move towards the open sea in summer, presumably driven by reproductive needs. Blue crabs in S’Ena Arrubia remained active also in winter with no hibernation, as opposed to crabs living in the colder areas of the native range along the eastern coast of the United States. Using acoustic telemetry, this study provides valuable information about the current knowledge on the movement ecology of the Atlantic blue crab, offering fine-scale movement data and an estimation of home range that may inform future studies and management approaches in other shallow, semi-enclosed lagoons of the Mediterranean Sea.</p>