The present study aimed to identify, classify, and compare participant-related limitations reported in doctoral dissertations in Translation Studies. The study employed a descriptive design and qualitative content analysis of 17 doctoral dissertations involving human participants, including 11 from Allameh Tabataba’i University (ATU) and 6 from the University of Isfahan, completed between 2021 and 2026. Participant-related limitations were coded thematically at the unit level using MAXQDA and organized into six overarching themes. Sample, participants, and linguistic and professional scope was the most pervasive theme across both universities. At ATU, sample size and linguistic scope limitations each accounted for 15.79% of the identified limitations, whereas this theme accounted for 50% at the University of Isfahan. Methodological and design limitations were reported in 80% of dissertations from ATU and 83.3% from the University of Isfahan. The findings suggest that participant-based research involves interconnected methodological challenges, from participant selection and access to data collection and research design. The findings indicate that sample adequacy is multidimensional, encompassing participant number, representativeness, experiential diversity, target-population fit, linguistic and professional scope, and research context. Mapping these limitations helps researchers anticipate methodological risks and make informed decisions before data collection.