Introduction: The association of partner autonomy support with women’s motivation for healthy eating, weight-related health behavior change, and psychological well-being has been largely overlooked. Results of 2 studies showed that the positive association between autonomy support and a variety of motivational and psychological outcomes was especially pronounced for women with high body mass index (BMI) (+1 SD) compared to low BMI (−1 SD). Method: In Study 1, autonomy support was measured as male partners’ report of their behavior in a cross-sectional design. In Study 2, autonomy support was measured as female participants’ perceptions of their partners’ behavior in a longitudinal home environment–based behavioral weight loss intervention. Results: Study 1 showed that autonomy support from partners was associated with greater self-determined motivation for healthy eating and self-reported well-being among women with higher BMI. Study 2 showed that changes in partner autonomy support over 18 months of a home-based weight loss intervention were associated with increases in motivation for treatment and greater weight loss, especially for women who had higher baseline BMI. Discussion: Both studies demonstrated that autonomy support was associated with adaptive functioning across weight status but that it was especially potent for women with higher BMI. This pattern of findings is explained in terms of the pressures women with higher BMI may feel about their weight-related behaviors.