Abstract: This study aimed to investigate differences in the sense of belonging and loneliness among U.S. Army active-duty soldiers and veterans. A total of 22 active-duty soldiers and 56 veterans were recruited through social media and professional contacts. The Sense of Belonging Instrument—Psychological Experience (Hagerty et al., 1992) was used to measure the sense of belonging, while the UCLA Loneliness Scale Version 3 was used to assess levels of loneliness. An independent sample t-test was used to compare differences in mean scores, and a moderated regression was conducted to evaluate the interaction of active-duty military service history. The statistical analysis revealed no significant differences in the sense of belonging and loneliness between active-duty soldiers and veterans, nor any significant interaction with military service history. Despite these findings being inconsistent with previous studies, further investigation into the sense of belonging in military culture is necessary to address loneliness.