Ractopamine hydrochloride (R) is commonly used in the livestock industry, mainly in pork and beef, to improve feed efficiency and productivity. In the present study, the use of R at different doses (20 ppm, 30 ppm, or 40 ppm) on growth performance and carcass characteristics of guinea pigs (male and female) was explored with a view to achieving greater use of this species for human consumption. Thirty-two clinically healthy guinea pigs at an average age of 5 weeks were used. The daily gain, feed over gain ratio, Kleiber ratio, carcass yield, and muscle thickness of the thigh in millimeters were measured. The results obtained were compared to a control group treated with only purified water, without R. Arithmetically, the measured variables showed benefits in the groups treated with R, with the results of Kleiber ratio and muscle thickness of the right thigh demonstrating statistical significance (P < 0.05). In the present work, the noncastrated males treated with R exhibited a more positive effect than the females (P = 0.006). The results suggest that the use of R as a growth promoter could benefit the productivity of guinea pigs for human consumption.