Purpose: The purpose of this study was to provide a preliminary characterization of new-onset abdominopelvic pain reported by trans-masculine persons after initiation of testosterone gender-affirming hormone therapy (GAHT). Methods: From December 2015 to February 2017, an anonymous survey was distributed through social media, listservs, and community centers to trans-masculine persons, 18 years or older, on testosterone GAHT, who experienced new-onset abdominopelvic pain after initiating GAHT. Results: Of the 183 persons who completed the survey, 127 (69.4%) endorsed new-onset abdominopelvic pain since the initiation of testosterone GAHT. Median interval from testosterone initiation to pain onset was 1 year (range: 1 month to 20 years). The majority of respondents reported pain that was intermittent (79.5%), cramping in nature (75.6%), and localized to the suprapubic region (78.7%). Those with a uterus and ovaries were 9.50 times (95% confidence interval 2.85-31.66) more likely to endorse suprapubic localization (as opposed to other abdominopelvic regions). All 28 respondents who reported pain resolution with treatment, identified this treatment as a hysterectomy. Conclusion: In this preliminary evaluation of new-onset abdominopelvic pain experienced by trans-masculine persons after the initiation of testosterone GAHT, the combination of suprapubic localization of pain with self-reported effectiveness of hysterectomy as treatment suggests a reproductive organ etiology. Based on our data, clinicians should be aware of the possibility that trans-masculine persons may present for this concern. This study offers a starting point for research. Further prospective studies are necessary to evaluate the incidence, cause(s), and the most appropriate interventions.