Conventional diagnostic systems struggled to meet the fluctuating demand for testing across the different waves of the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to assess the feasibility and effectiveness of the walkthrough (WT) approach in extending access to COVID-19 testing to high-risk populations traditionally underrepresented at health facilities (HFs) and to observe its impact on testing demand. An interventional study was implemented in markets (WT markets) and ports (WT ports) in Maputo City and Province, Mozambique. Demographic, epidemiological, and clinical data were collected for patients testing for COVID-19 in HFs and at WTs, and a nasal swab COVID-19 antigen rapid diagnostic test (Ag-RDT) was administered. Overall, testing rates at WTs were higher than those at HFs. At WTs, 4,452 of 4,457 participants were eligible and screened for COVID-19. Most participants were fully vaccinated for COVID-19 and had no symptoms or comorbidities (62.1% at WT markets and 87.9% at WT ports). During the baseline phase, the incidence testing rate of Ag-RDTs in intervention health facilities near the WTs was approximately one-fifth (P <0.001) of that in the control HFs located far from the WTs. In the control HFs, the incidence testing rate decreased significantly during the intervention period, whereas in intervention HFs, the incidence testing rate increased by approximately four times (P = 0.005). During times of low positivity rates and limited patient flow, the WT testing points may not yield the expected results in lowering the incidence testing rate within HFs. The WT may constitute an alternative approach to increasing the screening of infectious and noncommunicable diseases.