Musculoskeletal injuries (MSKIs) pose a significant threat to military readiness and are difficult to monitor due to Soldiers' reluctance to seek medical treatment. There is high risk of developing MSKIs while going through initial entry training (IET), many of which go unreported. The purposes of this study were to identify the contributing factors that influence US Army trainees to not seek medical care for self-reported symptoms of musculoskeletal injury (SMSKI) and establish how those factors may differ by sex, training school, and installation site. Data were collected from 739 trainees (607 males, 132 females) completing IET at either Fort Benning, GA, Fort Sill, OK or Fort Leonard-Wood, MO, USA. Male trainees were in combat arms jobs while female trainees were from both combat arms and other physically demanding jobs. All surveys were completed within 5 weeks of graduation from Advanced Individual Training and One Station Unit Training. Trainees answered a series of questions about SMSKIs sustained during IET that lasted seven or more days. Using a Likert-type scale (1-strongly disagree through 5-strongly agree), trainees rated the influence that each of the following seven statements contributed to their decision not to seek medical care: "graduating on time," "avoiding negative perceptions associated with injuries," "avoiding profile," "inconvenience in seeing a provider," "self-managing the injury based on past experience," "severity of the injury," and "prior negative experiences seeking medical care in the military." Pearson's Chi-square test was used to assess significant relationships among SMSKI reporting across sex, training school and training installation. Overall, SMSKI incidence was 36.1% and 58.3% among IET male and female trainees, respectively (40% overall). Nearly two-thirds (64%) of all trainees injured during IET had a SMSKI that they did not report to leadership or a medical provider. Across sex, female trainees were more likely to report SMSKIs than male trainees (p < 0.01), but there was no difference in SMSKI reporting rates by sex (p = 0.48). There was a difference in SMSKI rates by training school (p < 0.01), where infantry had higher SMSKI rates than field artillery (p < 0.01). There were no differences across training schools in how often trainees sought medical care (p = 0.58). The most common reasons selected for not reporting SMSKIs (i.e., not seeking medical care) included "I wanted to graduate on time" and "I wanted to avoid a profile." "I had prior negative experiences seeking medical care in the military" was consistently rated as the least important reason. Female trainees were more likely to not report SMSKIs in order "to avoid a profile" than male trainees (p < 0.05). Over 64% of trainees' did not seek medical care for their SMSKI during IET. As early detection, better reporting and timely treatment may result in reductions in SMSKI severity, reduced IET attrition, and lower medical expenses, trainees should be encouraged to report SMSKIs for proper early stage treatment. These study findings could be used to assist military leadership to create a positive environment for reporting and seeking care for SMSKIs.