Young bulls of lean continental cattle breeds raised on concentrates achieve high weight gains during fattening but may yield carcasses with low fat cover, which may have negative effects on meat quality. Fattening steers or heifers might be an alternative for these systems, but few studies have analysed in lean breeds the impact of castration of bulls at a similar BW or the performance of females. The aim of the trial was to characterise the growth, carcass and meat quality of bulls, steers and heifers of Pirenaica breed (lean beef breed) fed on concentrates and straw until a common body weight (475 kg). Bulls had greater weight gains than steers and heifers throughout the fattening period (P < 0.001). Bulls had greater plasma IGF-I concentration throughout the fattening period but lower leptin concentration from 400 kg onwards than steers and heifers when compared at the same BW. Regarding metabolites, the concentrations of glucose, beta-hydroxy-butyrate, urea and non-esterified fatty acids evolved differently in bulls, steers and heifers. At slaughter, steers and heifers had deposited more fat than bulls without other differences in carcass morphology. Regarding meat quality, meat of heifers had greater lightness and lower yellowness, chroma and hue value than that of bulls and steers. Meat shear force only tended to be different amongst sexes after 14 days of ageing (P < 0.10). Heifers had greater intramuscular fat content than steers and bulls. Total saturated fatty acids were similar amongst groups but monounsaturated fatty acids proportion was greatest in heifers, intermediate in steers and lowest in bulls. Polyunsaturated fatty acid proportion was greater in bulls than in steers and heifers. Only minor effects of sex were detected by the sensory panel, with more desirable flavours and higher tenderness in heifers. Therefore, despite the faster growth of entire bulls, fattening steers and especially heifers can lead to improved fat-related meat quality traits in lean breeds.