Background: The high prevalence of chronic obstructive pulmonary disease (COPD) in coronary artery disease (CAD) has been acknowledged over the past decade, although the cause/s remain uncertain due to differences in diagnoses. COPD has also become a leading CAD comorbidity, although again little is known about its interactions. This meta-analysis explored COPD prevalence in the global CAD population, as well as the influence of COPD on CAD. Methods: PubMed, Web of Science, Embase, and grey literature were searched until 26th November 2021. The prevalence of COPD was calculated, and data were grouped according to COPD diagnostic methods, interventions, region, economic status, etc. Outcomes including all-cause death, cardiac death, myocardial infarction, revascularization, stroke, heart failure, and respiratory failure were analyzed. This study was registered with PROSPERO (CRD No.42021293270). Results: There was an average prevalence of 14.2% for COPD in CAD patients (95% CI: 13.3–15.1), with diagnostics of COPD through spirometry, International Classification of the Diseases (ICD codes), and self-reported methods. Comorbid COPD–CAD patients were more likely to be smokers and suffer from cardiovascular and respiratory complications (all odds ratios [OR] >1). COPD–CAD has higher mortality (hazard ratio [HR] 2.81, 95% CI: 2.40–3.29), and myocardial infarction, stroke, and respiratory failure rates (all HR >1). Coronary artery bypass graft (CABG) reduces the need for revascularization (HR 0.43, 95% CI: 0.20–0.94) compared to percutaneous coronary intervention (PCI), without increasing mortality. Conclusions: The global prevalence of COPD is particularly high in CAD patients. COPD–CAD patients are more likely to encounter cardiovascular and respiratory complications and endure poorer outcomes. Limited evidence suggests that CABG may reduce the need for revascularization without increasing mortality, although further research is required to confirm these observations.