Background: Muscle energy techniques (METs) are manipulative interventions under current investigation for their impact not only within the musculoskeletal domain, but also in chronic obstructive pulmonary disease (COPD) patients. Previous research reported beneficial effects from a 4-week MET program on pulmonary function, functional capacity, and daily activities. Patients diagnosed with COPD are categorized using the Global Initiative for Chronic Obstructive Lung Disease (GOLD) strategy, to guide tailored treatment regimens for different COPD phenotypes. Given positive outcomes from the MET program across all COPD classifications, investigating outcomes with the different traditional GOLD stages seemed warranted. Materials and methods: A parallel-group, randomized controlled trial was adopted. A total of 108 participants with COPD were recruited and randomly assigned to the intervention or control group. All patients were classified by the GOLD classification. The intervention group received MET interventions, three-times weekly for 4 consecutive weeks, while the control group continued with their standard medical treatment. The study is clinically registered (clinicaltrials.gov identifier: NCT04773860). Results: All 108 patients completed the program, showing significant improvements across all three GOLD classifications. A significant difference in forced expiratory volume in 1 second (FEV₁) was reported across the three GOLD classifications at both time points (p < 0.001). The changes observed in forced vital capacity (FVC) measures displayed significant differences at week 0 when comparing all three groups (p = 0.039). No statistically significant differences were observed in the other outcome measures. Conclusion: A 4-week MET program resulted in more significant improvements in lung function measures among more severe COPD patients, whereas no substantial improvements were observed in chest measurements, activities of daily living (ADLs), or exercise tolerance tests when examining the different GOLD stage groups. Clinical significance: This study shows benefits of a 4-week MET intervention period on patients suffering from COPD, which led to statistically significant improvements resulted within the pulmonary function measures, chest expansion and ADL performance, and improvement in walking distance. All these outcome measurements provide evidence that this technique can be an effective treatment which can be used as an adjunct with other nonpharmacological physiotherapeutic treatments offered to these patients. Analysis per GOLD classification did not result in any differences between the groups based on COPD severity.