Objective: This study aimed to develop a self-report Likert scale measuring self-help group support perceived by mothers of elementary school children and to examine the validity and reliability of the scale. Methods: A total of 58 preliminary items were developed based on a literature review and individual interviews with 34 mothers of elementary school-aged children in Busan, South Korea. Following expert review, 48 items were retained. Exploratory factor analysis (EFA) was conducted using SPSS 30.0 with data from 264 mothers in Busan, followed by confirmatory factor analysis (CFA) using AMOS 30.0 with a nationwide sample of 288 mothers. The validity and reliability of the scale were subsequently examined. Results: The mother-perceived self-help group support scale comprised 20 items across three factors: emotional support (10 items), informational support (6 items), and child peer relationship support (4 items). The model demonstrated good fit, and reference validity and internal consistency were secured. Conclusions: This study examined the characteristics of self-help group support as perceived by mothers and developed and validated a measurement scale for this construct. The findings provide foundational data for strengthening support systems within self-help groups and promoting sustained participation among mothers.