The objective of the study was to determine some parameters of the meat quality of pontian monkey goby (Neogobius fluviatilis Pallas), an alien fish species in the Polish ichthyofauna, fished in the Vistula River. The fish were divided into age-based groups. Muscle samples (flesh and skin) for analyses were taken from the large side muscle of the fish body above the lateral line. The content of protein, fat, fatty acids, cholesterol, and water were determined in the meat. The mean content of fat was between 1. and 1.13 % and that of total cholesterol between 74.28 and 79.94 mg·100 g^-1. In the case of those two parameters, no statistically significant differences (p ≤ 0.05) were reported among the fish individuals showing different body length. Statistically significant differences (p ≤ 0.05) were determined in the mean content values of protein (18.52 – 21.06 %) and water (77.98 – 78.74 %) in the meat of fish of different body length. The percent content of PUFA was the highest (from 39.90 to 40.80 % of all the fatty acids); the content of the MUFA determined was the lowest (from 25.98 to 28.78 %). In the group of SFA, the content of C16:0 acid was the highest, in the group of MUFA, the highest content was that of C18:1 n-9, and in the group of PUFA that of C20:5 n-3. The n-3 / n-6 ratio ranged from 1.33 and 1.44 and no statistically significant differences (at p ≤ 0.05) were found between the individuals of different body length. The AI and TI values ranged from 0.39 to 0.42 and from 0.31 to 0.32, respectively.