Abstract Background Cardiac surgery causes pathophysiological changes that favor the occurrence of pulmonary and functional complications. Objective To investigate the effects of inspiratory muscle training (IMT) with an electronic device on patients undergoing cardiac surgery. Methods A randomized controlled trial was conducted with 30 adult patients undergoing elective cardiac surgery. A control group (CG) received conventional physical therapy care, and an intervention group (IG) received IMT using the POWERbreathe K5® electronic device. Two daily sessions of physical therapy were performed at the intensive care unit and one daily session at the ward until the sixth postoperative day. The following variables were measured preoperatively and on the sixth postoperative day, in both groups: inspiratory muscle strength, dynamic inspiratory muscle strength, and peak inspiratory flow. Data distribution was evaluated by the Shapiro-Wilk test. Analysis of variance was used, and the results were considered statistically significant when p < 0.05. Results Maximal inspiratory pressure (71.7 ± 17.1 cmH2O vs 63.3 ± 21.3 cmH2O; p = 0.11], S-index (52.61 ± 18.61 vs 51.08 ± 20.71), and peak inspiratory flow [(2.94 ± 1.09 vs 2.79 ± 1.26)] were maintained in the IG but had a significant reduction in the CG. Conclusion IMT performed with an electronic device was effective at maintaining inspiratory muscle strength, dynamic inspiratory muscle strength, and peak inspiratory flow when compared to conventional physical therapy. Int J Cardiovasc Sci. 2020; [online].ahead print, PP.0-0