Purpose: Few trials have aimed to promote diet and exercise behaviors in both cancer survivors and their family members and examine their associations with weight-related outcomes. We conducted a secondary analysis to examine associations between change in diet and exercise behaviors and weight-related outcomes for overweight breast cancer survivors and their overweight adult daughters in the Daughters And MothErS Against Breast Cancer (DAMES) randomized trial. Methods: The DAMES trial assessed the impact of two iteratively tailored, mailed print diet and exercise interventions against standard brochures over a 12-month period. This analysis examined change in diet and exercise behaviors and weight-related variables from baseline to post-intervention for the 50 breast cancer survivors and their adult daughters randomized to the intervention arms. To reduce the potential for type II error in this pilot, p values <0.10 were considered statistically significant. Results: For mothers, change in diet quality was uniquely related to change in BMI (β = −0.12, p = 0.082), weight (β = −0.12, p = 0.060), and waist circumference (β = −0.38, p = 0.001), whereas change in caloric intake was related to waist circumference (β = 0.21, p = 0.002). For daughters, change in caloric intake was related to change in waist circumference (β = 0.12, p = 0.055). However, change in diet quality was not associated with weight-related outcomes in daughters. Additionally, change in exercise was not associated with weight-related outcomes in mothers or daughters. Conclusions: Findings support mail-based and other tailored interventions for weight loss in this population, with an emphasis on diet quality for breast cancer survivors and caloric intake for their adult daughters.