Background: Routine immunization programs in Pakistan rely heavily on estimated population denominators, limiting accurate identification and follow-up of zero-dose and under-immunized children, particularly in high-risk urban settings such as Quetta, Balochistan. Methods: A quasi-experimental, pre–post implementation study was conducted from June 2024 to June 2025 across three low-performing union councils. A CHW-based household tracking tool was integrated within existing PEI–EPI systems. Data were derived from CHW Books, Rapid Convenience Assessments (RCA), and routine MIS reports. Descriptive statistical analysis was employed to assess trends in immunization coverage and program performance; no inferential statistical tests were applied due to the use of complete programmatic (census-based) data rather than sampled observations. Results: Antigen-specific coverage improved substantially, with Penta-3 coverage increasing from 22% to 95%, zero-dose conversion from 45% to 65%, and defaulter follow-up from 14% to 79%. All three union councils transitioned to Category 1 operational status. Administrative coverage exceeding 100%, reflecting population-level coverage and denominator correction rather than true population-level coverage. Conclusions: Integrating CHW-based tracking with dynamic denominator verification enhances routine immunization, microplanning, equity, and operational performance in high-risk LMIC urban settings.