The aim of this study is to evaluate and compare the performance of two different types of cotton pickers, namely the John Deere model 7260 and the Pamuk brand cotton harvesting machine model ptm2. Therefore, field experiments were conducted to investigate the effects of four mean forward speeds of 1.32 ,1.66, 1.87, and 2.15 km h^-1, three fiber moisture contents of 13.3, 10.8, and 8.7% d.b, and three inter-row spaces of 0.70, 0.76, and 0.85 m. on the picking losses, machine productivity, specific energy consumption and fiber physical properties. The results showed that the minimum values of the picking losses were 0.8 and 4.5 % for the John Deere and Pamuk cotton pickers respectively recorded at a forward speed of 1.32 km/h, a fiber moisture content of 10.8% d.b., and an inter-row spacing of 0.85 m. The maximum values of machine productivity of the John Deere and Pamuk cotton pickers were 2.1 and 0.995 Mg h^-1, respectively, at a forward speed of 2.15 km h^-1, a fiber moisture content of 10.8%, and an inter-row spacing of 0.76 m. The lowest values for the specific energy consumption were 23.07 and 30.69 kW h Mg^-1 for the John Deere and Pamuk cotton pickers, respectively, at a forward speed of 2.15 km/h, a fiber moisture content of 8.7 % d.b., and an inter-row spacing of 0.85 m. Also, At a forward speed of 1.32 km/h, fiber moisture content of 13.3% and an inter-row spacing of 0.76 m. both cotton pickers achieved the maximum values of 2.5% span fiber length, 50 % span fiber length, fiber length uniformity ratio and reflectance and minimum values of seed cotton trash content and yellowness.