Supported by considerable public investment through post-9/11 higher education benefits, student military service members/veterans (SSM/ Vs) have been one of the fastest-growing groups of nontraditional students in American universities in recent years. Despite their increased numbers and potential to diversify science, technology, engineering, mathematics, and medical (STEMM) fields, little research has explored SSM/V academic development and success across university STEMM contexts. This mixed methods study used social capital theory to explore links between STEMM SSM/V social support and a sense of campus belonging--shown to be important to achievement among traditionally marginalized college students--within 4-year campus communities. Social network analyses of surveys indicated that larger SSM/V support networks, including on-and off-campus social ties as well as student and university educator ties, positively correlated with campus belonging. Social support networks with military ties, traditionally seen to benefit SSM/V college integration, did not correlate. Interview responses suggested that while belonging can be discouraged among SSM/Vs by military-associated STEMM imposter feelings, it is fostered through student friendship, faculty care, and veteran-focused campus support. Results underscored the importance of authentic interaction as well as purposeful efforts to bring SSM/Vs together with fellow students, educators, and staff.