Human resource management (HRM) in the public sector plays a pivotal role in enhancing the effectiveness of public organizations and advancing good governance. Despite the quantitative expansion of research in this field in Iran over the past decade, the methodological quality of these studies has rarely been evaluated systematically. The aim of this study is to provide a critical review of the methodological literature on public sector HRM, with a particular focus on Iran, and to identify its major gaps. Adopting a semi-systematic review approach and guided by the PRISMA 2020 framework, this study examined 128 selected sources—out of an initial 520 records—including 75 international studies and 53 Persian/Iranian studies, using descriptive and critical analysis. The findings reveal that existing research is predominantly quantitative, cross-sectional, and reliant on self-reported data. Common-method bias control is seldom reported, and longitudinal, multilevel, and genuinely integrated mixed-methods studies are nearly absent. Moreover, the use of emerging data-driven methodologies is not evident in the domestic literature, indicating a substantial methodological gap compared with global standards. The results suggest that these challenges stem from institutional and educational constraints, which in turn undermine the production of credible knowledge and evidence-based policymaking. Accordingly, strengthening longitudinal and mixed-methods research, leveraging secondary data, and reforming methodological training are proposed as key pathways for enhancing methodological rigor and advancing applied knowledge in this field