ABSTRACT: PURPOSE:This study evaluated the feasibility and preliminary efficacy of two 6-month, self-regulation interventions that focused on daily self-weighing (DSW) and used objective monitoring and tailored feedback about weight (±activity), to prevent weight gain among African American breast cancer survivors. METHODS:Participants (n = 35) were randomized to an intervention + activity monitoring (INT+), intervention (INT), or control (CON) group. Interventions included a wireless scale (±activity tracker) that transmitted objective data to a mobile app/website, emailed lessons, and tailored feedback based on objective weight (±activity data). Participants completed in-person and online assessments at baseline, 3 months, and 6 months. RESULTS:Ninety-four percent of participants completed assessments at 3 months, and 97 % at 6 months. Median (IQR) weight change after 6 months was -0.9 % (-4.4-0.1) in the INT+ (p = 0.075; p = 0.067 vs. CON) and -0.2 % (-4.2-1.3) in the INT groups (p = 0.463; p = 0.357 vs. CON), versus a 0.2 % (-0.7-1.7) gain in the CON group. The proportion of INT+, INT, and CON participants that were at or below baseline weight was 72.7, 53.8, and 45.5 %, respectively (effect sizes d = 0.64, d = 0.18). Most INT+ participants weighed and wore trackers ?5 days/week (INT+, 81.9 % vs. INT, 38.5 % vs. CON, 0 %; p < 0.0005; INT+, 72.7 %). Both intervention groups perceived DSW as positive, and 100 % would recommend the program to other breast cancer survivors. CONCLUSION:An intervention focused on DSW as a self-monitoring strategy shows promise for preventing weight gain in breast cancer survivors. IMPLICATIONS FOR CANCER SURVIVORS:Daily self-monitoring of weight and activity may be a feasible and accessible approach to promote weight gain prevention in breast cancer survivors. CLINICAL TRIAL REGISTRATION:ClinicalTrials.gov, NCT02030353.