The aim of this study was to determine changes in selected growth parameters of farm-raised mallard ducklings from hatch to 42 d of age. The largest increases in body and carcass weights of ducklings and weights of the analyzed tissue components were noted during the first 28 d of the rearing period, except for breast and wing muscles. In comparison with other muscle groups, the growth rate of breast and wing muscles was lower from hatch to 14 d of age, greatest between 14 and 28 d, and remained high up to 42 d of age. The average body weight of mallard ducklings increased more than 16-fold (from 39.7 to 644.8 g, P ≤ 0.01), and the average carcass weight increased more than 26-fold (from 14.4 to 384.5 g, P ≤ 0.01). The growth rates of carcass and tissue components varied considerably. Wing weight increased 84.5-fold (from 0.80 to 67.6 g, P ≤ 0.01), followed by breast weight, which increased 48-fold (from 1.7 to 82.9 g, P ≤ 0.01). Slower growth rates were noted in the remaining carcass parts: back, 23-fold; neck, 19.2-fold; and legs, 17.1-fold (from 5.4 to 92.2 g, P ≤ 0.01).