The National Diabetes Prevention Program (NDPP) is the most widely available behavioral intervention to prevent diabetes, but attrition is a concern and strategies are needed to make the program more engaging. Previous evidence suggests that the 150-min weekly physical activity goal in NDPP is hard for many to achieve. Further study of the impact of this protocol recommendation may improve understanding for NDPP reach and effectiveness in reducing diabetes risk. We conducted an observational study of relationships between physical activity goal attainment and retention and weight loss among 391 NDPP participants between March 2013 and May 2016. Average percent of self-reported weekly physical activity goal attainment was 52.7% (SD = 35.1). Goal attainment was related to percent of sessions attended, β = 0.21 (p < .01) and program completion (OR 0.47; p < .05; 95% CI 0.24-0.90). Each occurrence of goal failure was associated with a 25% lower likelihood of attending the next session (OR 0.75; p < .001; 95% CI 0.64-0.87). Goal attainment was also related to total percent weight loss, β = -0.14 (p < .05) and achieving ≥5% weight loss (OR 0.39; p < .01; 95% CI 0.19-0.76), but there was no effect of goal attainment on weight change per session attended. Failing to attain physical activity goals may deter retention in the NDPP. Yet, goal attainment did not affect the rate of weight loss per session attended. It may be important to encourage continued engagement among individuals who struggle to achieve physical activity goals. Moreover, it may be necessary to modify physical activity recommendations to meet individual needs.