OBJECTIVE To evaluate the effects of resistance exercise applied early after coronary artery bypass grafting. METHODS It is a randomized controlled trial with 34 patients undergoing coronary artery bypass grafting between August 2013 and May 2014. Patients were randomized into two groups by simple draw: a control group (n=17), who received conventional physical therapy and an intervention group (n=17), who received, additionally, resistance exercise. Pulmonary function and functional capacity were evaluated in preoperative period and hospital discharge by spirometry and the six-minute walk test. For statistical analysis, we used the following tests: Shapiro-Wilk, Mann-Whitney, Student'st and Fisher's exact. Variables with P<0.05 were considered significant. RESULTS Groups were homogeneous in terms of demographic, clinical and surgical variables. Resistance exercise exerted no effect on pulmonary function of intervention group compared to control group. However, intervention group maintained functional capacity at hospital discharge measured by percentage of predict distance in 6MWT (54.122.7% vs. 52.515.5%,P=0.42), while control group had a significant decrease (59.211.1% vs. 50.69.9%, P<0.016). CONCLUSIONS Our results indicate that resistance exercise, applied early, may promote maintenance of functional capacity on coronary artery bypass grafting patients, having no impact on pulmonary function when compared to conventional physical therapy.