This study aimed to investigate the effects of adding positive expiratory pressure (PEP) and breath stacking (BS) training to routine chest physical therapy after cardiac surgery on pulmonary function (PF), respiratory muscle strength (RMS), and chest wall expansion (CWE) in comparison to receiving routine chest physical therapy alone. Thirty-four cardiac surgery patients were assigned randomly to either the PEP (n=10), BS (n=12), or control group (CON) (n=12). All participants received routine chest physiotherapy. The PEP training consisted of 5 breaths/set, 6 sets/session, 2 sessions/day for three days postoperatively via a BreathMAX device, while the BS training involved 5 breaths/set, 3 sets/session, 2 sessions/day for three days postoperatively. All participants were assessed for PF, RMS, and CWE. Results showed that after training, all groups showed a significant increase in force vital capacity, vital capacity, total lung capacity, and CWE (p-value < 0.01) compared to postoperative day 2. The PEP and CON groups also exhibited a significant increase in peak expiratory flow rate and forced expiratory volume in one second. Moreover, a significant increase in maximal inspiratory pressure and maximal expiratory pressure on postoperative day 5 was observed in the BS and CON groups compared to postoperative day 2. However, no significant differences between the groups were found. The three protocols were equally efficacious concerning PF recovery during the first 5 postoperative days. When compared with routine therapy, BS tended to yield greater RMS. Meanwhile, PEP tended to produce better PF and CWE than the other two techniques. Therefore, physiotherapists should consider post-operative management as a key role in these patients, especially when using the chest physical therapy technique, since this technique has different method and is beneficial for the reduction in post-operative complications.