Objectives: Endometrial cancer (EC) survivors are often overweight or obese and may benefit from increased physical activity. Increases in daily step count of 2,000 steps per day has been shown to improve cardiovascular health. We sought to assess a fitness intervention (fitness tracker + tailored feedback messages) for EC survivors. Methods: A prospective trial of EC survivors was undertaken from September 2018 to December 2019. Thirty-nine survivors were approached for enrollment with 36 randomized (18 intervention, 18 control). All participants received a fitness tracker. Survivors were randomized 1:1 to receipt or non-receipt of weekly tailored feedback messages. The primary outcome was change in average daily step count from baseline (week 1) to study completion (week 12). Secondary outcomes included acceptability, and changes in metabolic lab parameters (serum glucose, LDL, and insulin levels), body mass index (BMI) and waist to hip ratio (W/H). The trial was powered to detect a clinically significant change in daily step count of 2,000 steps. Comparisons of baseline to study completion labs were made using the Wilcoxon Two-sample test. Student's T-test was used for comparisons of control and intervention groups. Results: At baseline, there was no difference in BMI (35.9 vs 36.7, p=0.81) or W/H ratio (0.9 vs 0.89, p=0.40) between control and intervention arms. Baseline daily step count was 5291 steps in the control arm and 4295 in the intervention arm (p=0.16). There was no difference in baseline metabolic labs including glucose (100 vs 103, p=0.85), serum insulin (13.1 vs 16.8, p=0.78), and LDL (150 vs 113, p=0.07). The intervention group saw a statistical change in average daily step count (4295 to 5332, p=0.02). The control group did not have a statistically significant change (5291 to 5600, p=0.40). For the primary outcome of average daily step count change, there was no statistically significant difference between the two groups (+309 control vs +1037 intervention, p=0.21). There was no difference in change in BMI (-0.27 vs -0.02, p=0.7), glucose (+1 vs -3, p=0.29), LDL (-9.1 vs -3.5, p=0.95) or insulin (-2.15 vs -1.95, p=0.32) between the control and intervention arms. Regarding acceptability, survivors found the feedback to be helpful (87%) and easy to understand (87%). Two-thirds of survivors found the messages to be motivating, 47% desired increased frequency of messaging, and 53% thought the weekly message was adequate. Overall, 33% of intervention survivors versus 22% of control survivors had decline in fitness tracker use during the intervention, resulting in missing step data (p=0.46). Conclusions: A fitness intervention using fitness trackers and tailored feedback messaging may improve physical activity as measured by daily step count in EC survivors, however, significant noncompliance with fitness tracker use was seen in both groups by study end. Tailoring the frequency of feedback messages to survivor preference may be important to optimizing this intervention.