Despite the benefits of physical activity for breast cancer survivors, the majority remain insufficiently active. Mobile health (mHealth) physical activity interventions may be a more scalable strategy to increase activity among survivors. However, little is known about their preferences for mHealth intervention features. This study explored survivors' preferences for these features. Survivors (N = 96; Mage = 55.8 (SD = 10.2)) self-reported demographic and disease characteristics, physical activity. A subset (n = 28) completed a semi-structured phone interview. Transcribed interviews were evaluated using a thematic content analysis approach and consensus review. Following interviews, the full sample self-reported interests and preferences for intervention features via online questionnaires. Quantitative data were analyzed using descriptive statistics. Five themes emerged from interview data: (1) importance of relevance to breast cancer survivors; (2) easy to use; (3) integration with wearable activity trackers; (4) provide sense of accomplishment; and (5) variability in desired level of structure and personalization. The highest ranked intervention features were: daily and weekly progress feedback (87.5%), newsfeed (86.6%), activity challenges (81.3%), and scheduling tool (79.2%). Survivors were interested in receiving progress feedback (80.2%) and motivational (78.1%) and reminder (75.0%) messages. Breast cancer survivors are interested in mHealth physical activity promotion interventions, but preferences varied around themes of relevance, ease of use, and enhancing personal motivation. Engaging survivors in developing and implementing remotely delivered mHealth activity promotion interventions may enhance their effectiveness.