Purpose <p>To report prevalence rates and examine associations between loneliness and mental health conditions by residency status among graduate students.</p> Methods <p>Participants were 29,944 graduate students (including 5,671 international graduate students) attending universities in the United States. Residency status was dichotomized as either international or domestic. Loneliness and mental health conditions (symptoms of depression, anxiety, and suicidal ideation) were self-reported measures using validated measures and established cutoff criteria. We performed descriptive analyses and used multivariate regression to examine associations between loneliness and mental health outcomes, stratified by residency status.</p> Results <p>International graduate students experienced greater symptoms of anxiety for each one unit increase of loneliness, compared to domestic graduate students (<i>β</i>: 0.14, 95% CI: 0.06–0.21). Additionally, each one-unit increase in loneliness was associated with 1.63 times greater odds of suicidal ideation among international graduate students (<i>p</i> &lt; 0.001), and 1.60 times greater odds of suicidal ideation among domestic graduate students (<i>p</i> &lt; 0.001).</p> Conclusions <p>These findings show loneliness is a significant correlate of mental health among graduate students and the relationship between loneliness and anxiety differs by residency status.</p>