Background: Health behaviors, such as diet and exercise, are actions individuals take that can potentially impact gastrointestinal (GI) symptoms and the gut microbiota. Little is known about how health behaviours impact GI symptoms and the gut microbiota after anti-cancer therapies. Methods: This is a secondary analysis of a cross-sectional study that investigated relationships between GI symptoms, gut microbiota, and patient-reported outcomes in adult cancer survivors. Gut microbiota was assessed from stool samples using 16S rRNA gene sequencing. GI symptoms and health behaviors were measured via self-report. Descriptive statistics, linear regression, and correlation analyses are reported. Results: A total of 334 cancer survivors participated and a subsample of 17 provided stool samples. Most survivors rated their diet as moderately healthy (55.7%) and reported engaging in low intensity exercise (53.9%) for ≤5 hours/week (69.1%). Antibiotic use was associated with more belly pain, constipation, and diarrhea (p< .05). Survivors consuming a healthier diet had fewer symptoms of gas/bloating (p= 0.02). Better diet health was positively correlated with Lachnospiraceae abundance, and negatively with Bacteroides abundance (ps