Background: Lifestyle modification programs improve several health-related behaviors, including physical activity (PA) and nutrition. However, few of these programs have been expanded to impact a large number of individuals in one setting at one time. Therefore, the purpose of this study was to determine whether a PA- and nutrition-based lifestyle modification program could be effectively conducted using a large group format in a community-based setting. Method: One hundred twenty-one participants enrolled in a 16-week, community-based lifestyle modification program and separated in small teams of 13 to 17 individuals. Height, weight, fruit and vegetable (FAV) consumption, physical fitness, and several psychosocial measures were assessed before and after the program. Results. Significant improvements in 6-minute walk distance (+68.3 m; p < 0.001), chair stands (+6.7 repetitions; p < 0.001), FAV servings (+1.8 servings/day; p < 0.001), body weight (-3.2 lbs; p < 0.001), as well as PA social support and eating habits self-efficacy were observed. Our lifestyle modification program was also successful in shifting participants to higher levels of stages of change for nutrition and PA, increasing overall levels of self-efficacy for healthy eating, and improving levels of social support for becoming more active. Conclusions: A lifestyle modification program can be successfully implemented in a community setting using a large group format to improve PA and FAV attitudes and behaviors.