BACKGROUND: Survivors of rectal cancer experience persistent bowel dysfunction after treatments. Dietary interventions may be an effective approach for symptom management and posttreatment diet quality. SWOG S1820 was a pilot randomized trial of the Altering Intake, Managing Symptoms in Rectal Cancer (AIMS-RC) intervention for bowel dysfunction in survivors of rectal cancer. METHODS: Ninety-three posttreatment survivors were randomized to the AIMS-RC group (N = 47) or the Healthy Living Education attention control group (N = 46) after informed consent and completion of a prerandomization run-in. Outcome measures were completed at baseline and at 18 and 26 weeks postrandomization. The primary end point was total bowel function score, and exploratory end points included low anterior resection syndrome (LARS) score, quality of life, dietary quality, motivation, self-efficacy, and positive/negative affect. RESULTS: Most participants were White and college educated, with a mean age of 55.2 years and median time since surgery of 13.1 months. There were no statistically significant differences in total bowel function score by group, with the AIMS-RC group demonstrating statistically significant improvements in the exploratory end points of LARS (p = .01) and the frequency subscale of the bowel function index (p = .03). The AIMS-RC group reported significantly higher acceptability of the study. CONCLUSIONS: SWOG S1820 did not provide evidence of benefit from the AIMS-RC intervention relative to the attention control. Select secondary end points did demonstrate improvements. The study was highly feasible and acceptable for participants in the National Cancer Institute Community Oncology Research Program. Findings provide strong support for further refinement and effectiveness testing of the AIMS-RC intervention.