Menstrual hygiene management (MHM) remains a critical yet often neglected issue in humanitarian settings. Reusable menstrual underwear (MU) offers a sustainable option where disposable products are limited, but evidence from low-income settings is scarce. This mixed-methods study assessed MU acceptability and usability among adult women in Kalehe, Democratic Republic of Congo. Participants received four MU, a hygiene kit, and instructions, with follow-up after three months through a survey (n = 124), and focus group discussions (n = 9). MU was highly accepted, with 94.3% reporting satisfaction and 98.4% preferring it to their usual MHM method. Reported benefits included comfort, hygiene, and ease of use, while challenges included absorbency, insufficient quantity, drying, and durability. Participants recommended improving MU quality, tailoring sizing, and expanding distribution, especially to adolescents. Finding suggests MU is a feasible, acceptable MHM option in a low-resource, conflict-affected setting, warranting further evaluation as part of emergency kits for displaced populations.