The Atlantic blue crab Callinectes sapidus 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 (Sardinia, western Mediterranean). 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 in spring and summer. Females tended to move towards the open sea in summer, driven by reproductive needs. Compared to the native areas along the western Atlantic coasts, blue crabs in S’Ena Arrubia remained active also in winter with no hibernation. This study, which offers for the first time long-term data on the blue crab movement ecology, extends the knowledge of the species and may provide support to its management and control in invaded areas.