OBJECTIVE:To assess the cost of adopting a plant-based diet. METHODS:Breast cancer survivors randomized to dietary intervention (n=1109) or comparison (n=1145) group; baseline and 12-month data on diet and grocery costs. RESULTS:At baseline, both groups reported similar food costs and dietary intake. At 12 months, only the intervention group changed their diet (vegetable-fruit: 6.3 to 8.9 serv/d.; fiber: 21.6 to 29.8 g/d; fat: 28.2 to 22.3% of E). The intervention change was associated with a significant increase of $1.22/ person/week (multivariate model, P=0.027). CONCLUSIONS:A major change to a plant-based diet was associated with a minimal increase in grocery costs.