Background—Although numerous primary studies have documented the mental health benefits of physical activity (PA), no previous quantitative synthesis has examined anxiety outcomes of interventions to increase PA. Objectives—This meta-analysis integrates extant research about anxiety outcomes from interventions to increase PA among healthy adults. Method—Extensive literature searching located published and unpublished PA intervention studies with anxiety outcomes. Eligible studies reported findings from interventions designed to increase PA delivered to healthy adults without anxiety disorders. Data were coded from primary studies. Random-effects meta-analytic procedures were completed. Exploratory moderator analyses using meta-analysis ANOVA and regression analogues were conducted to determine if report, methods, sample, or intervention characteristics were associated with differences in anxiety outcomes. Results—Data were synthesized across 3,289 subjects from 19 eligible reports. The overall mean anxiety effect size (d-index) for two-group comparisons was 0.22 with significant heterogeneity (Q = 32.15). Exploratory moderator analyses found larger anxiety improvement effect sizes among studies that included larger samples, used random allocation of subjects to treatment and control conditions, targeted only PA behavior instead of multiple health behaviors, included supervised exercise (vs. home-based PA), used moderate or high-intensity instead of low-intensity PA, and suggested subjects exercise at a fitness facility (vs. home) following interventions. Discussion—These findings document that some interventions can decrease anxiety symptoms among healthy adults. Exploratory moderator analyses suggest possible directions for future primary research to compare interventions in randomized trials to confirm causal relationships.