Background: Primary health care centers (PHCs) face increasing demand, constrained staffing, and complex patient needs, contributing to delays, overcrowded clinics, missed appointments, and compromised patient experience. Interventions targeting patient flow and operational efficiency, such as open, advanced access scheduling, Lean process redesign, targeted reminders, and community-based models, reduce waiting time and improve satisfaction while maintaining safety. Objective: To synthesize evidence from original studies on patient flow and operational efficiency interventions in PHC, ambulatory primary care settings and evaluate effects on waiting time, access, safety, and satisfaction. Methods: A PRISMA-aligned systematic review was conducted using electronic databases as the full-text source. We included original interventional or quasi-experimental studies in PHC, primary care, ambulatory settings evaluating operational interventions with outcomes related to waiting time, access, safety, satisfaction, experience, or attendance. Ten original studies were included for results synthesis. Results: In included studies, open access scheduling reduced short-term appointment wait times but effects on satisfaction were inconsistent. Lean implementation reduced service waiting times and increased satisfaction in an ambulatory setting. Predictive-model–driven reminder strategies improved attendance and reduced no shows, supporting better clinic capacity utilization. Community paramedicine integrated with primary care showed system-level improvements in flow and safety-related processes in PHC. Interventions that combined demand–capacity matching (scheduling, access redesign) with targeted attendance supports (risk-based reminders) were most consistently associated with improved operational outcomes. Conclusion: PHC operational efficiency interventions can reduce waiting time and improve satisfaction or attendance, but effects vary by implementation stability, staffing resilience, and context. Risk-stratified reminders and structured process redesign are supported by consistent findings, while open access scheduling requires safeguards for sustainability and continuity.