This study assesses how an Integrated Management System (IMS) aligned with ISO 9001:2015 (quality), ISO 45001:2018 (occupational health and safety), and ISO 14001:2015 (environment) affects productivity in an outpatient healthcare setting. An 18-month, phased implementation consolidated governance, risk, and process control into a single architecture, replacing parallel programs with shared policies, integrated audits, and unified corrective-action workflows. Using a mixed-methods, pre–post design, we tracked key performance indicators—patient lead time, throughput per clinician hour, appointment punctuality, first-contact resolution, rework, incident and near-miss rates, absenteeism, energy and water intensity per visit, waste segregation, and cost-to-serve—while capturing staff and patient perceptions through surveys and focus groups. Interrupted time- series analyses revealed sustained improvements in operational flow and sched- ule adherence, reductions in clinical and occupational incidents, and lower re- source intensity per encounter. Financial analysis indicated cost avoidance and margin uplift associated with standardized work, clearer role accountability, and risk-based maintenance. Qualitative evidence highlighted a stronger safety culture, greater cross-functional problem solving, and higher employee engagement. Overall, implementing a tri-standard IMS as one coherent system—not three separate ones—delivered measurable gains in productivity, safety, and environmental performance, strengthening organizational resilience and regulatory compliance. The paper contributes a practical roadmap for outpatient providers, including a staged roll-out plan, a core KPI set for integrated oversight, and an audit cadence that links nonconformities to continuous-improvement projects with demonstrable operational impact.