The aim of this study was to determine the occurrence, spatial distribution and abundance pattern of the Harris mud crab <i>Rhithropanopeus harrisii</i> in the Gulf of Gdańsk (southern Baltic Sea). Between 2006 and 2010, this species was found at 69 out of 129 sampling stations, at depths from 0 to 20 m. Two main aggregations of the Harris mud crab were established: (1) in Puck Bay (max. density 19 indiv. 100 m<sup>-2</sup>) and (2) in the Gdynia and Sopot area (max. density 5 indiv. 100 m<sup>-2</sup>). 920 specimens were collected during the whole sampling period: 150 juveniles, 370 females and 400 males. The minimum measured carapace width was 1.96 mm, the maximum 21.40 mm (mean 9.03 ±4.11 mm)