Abstract Fatigue is a frequent and debilitating symptom of inflammatory bowel disease (IBD) and can include mental and physical exhaustion, tiredness, or weakness. Modifiable psychosocial factors, such as depression and anxiety, are associated with fatigue in IBD, and provide insight into potential treatment targets. However, little is known about distinct ways in which psychosocial factors relate to subtypes of fatigue. The current study examined associations between psychosocial factors and 5 fatigue subtypes: general, physical, mental, reduced motivation, and reduced activity. Patients 18 and above from Dartmouth-Hitchcock’s IBD Center with Crohn’s disease or ulcerative colitis were invited to participate in a survey via an electronic medical record system message. Measures included the Patient Reported Outcomes-3, Multidimensional Fatigue Inventory, Pain Catastrophizing Scale, Generalized Anxiety Disorder-7, Patient Health Questionnaire-9, Insomnia Severity Index, and Brief Pain Inventory. Five forward linear regressions were performed with step 1 including disease activity, step 2 including covariates (age, gender, IBD diagnosis) and step 3 allowing for the inclusion of insomnia, pain severity, depression, anxiety, and pain catastrophizing. Participants were 312 individuals above the age of 18 (M=48.62, SD=16.10). Participants were 66.3% women and 96.5% White. 60.9% were diagnosed with Crohn’s disease and 39.1% with ulcerative colitis. 54.8% were categorized as having active disease based on self-reported symptoms. For all five subtypes of fatigue, depression emerged as the most influential psychosocial predictor. Depression accounted for 21% of the variance in general fatigue, 14% in physical fatigue, 18% in activity avoidance, 19% in reduced motivation, and 29% in mental fatigue. Regarding differences among subtypes, insomnia was only significant in the model predicting general fatigue, accounting for an additional 2% of the variance, and anxiety was only significant in the model predicting activity avoidance, accounting for an additional 3% of the variance. In comparison, self-reported disease activity accounted for 23% of the variance in general fatigue, 7% in physical fatigue, 8% in activity avoidance, 12% in reduced motivation, and 10% in mental fatigue. Depression is a notable factor associated with all subtypes of fatigue in IBD, especially mental fatigue. There are differences in how psychosocial factors relate to fatigue subtypes such that anxiety is uniquely associated with activity avoidance and severity of insomnia is uniquely associated with general fatigue. Results suggest that assessment of fatigue in IBD should also include assessment of depression as standard of care. Additionally, helping patients engage in behavioral interventions to reduce depression, anxiety, and insomnia may be critical for managing fatigue. Results of forward regressions predicting fatigue subtypes