BACKGROUND Long-term patient survival after intestinal transplantation (IT) remains low compared with other organ transplants despite years of advancement in clinical experience. While patients with extremely high or low body mass index (BMI) are often considered ineligible for IT, the impact of BMI on post-transplant IT survival remains understudied. MATERIAL AND METHODS Using the United Network for Organ Sharing Standard Transplant database, we conducted a retrospective cohort study on patients who underwent IT between April 11, 1994, and September 29, 2021. We assessed the association of recipient and donor BMI at transplant with post-transplant mortality using Kaplan-Meier survival curves and univariate and multivariate Cox regression analyses. RESULTS A total of 1541 patients were included in our final sample. Of these patients, 806 were females (52.5%) and most were in the normal-weight BMI subgroup (54.2%). Obese class II (mean; 36.8±10.92 years) and underweight patients (mean; 37.6±13.37 years) were significantly younger than patients in other BMI categories. The adjusted multivariate model demonstrated an increased risk of mortality in underweight IT recipients compared to normal-weight IT recipients (aHR=1.25, 95% confidence interval [CI], 1.02-1.54; P=0.032).There was no significant association between donor BMI categories and survival in IT recipients. CONCLUSIONS Recipient BMI below normal is associated with an increased risk of mortality after intestinal transplantation and represents a potentially modifiable patient characteristic to improve survival outcomes.