Background <p>The last twenty years have seen a notable rise in mental health concerns among children and adolescents. These concerns were profoundly exacerbated by the COVID-19 pandemic, prompting the need for timely intervention.</p> Objective <p>The purpose of these studies was to evaluate the therapeutic potential of overnight summer camp.</p> Methods <p>(1) A systematic review of the literature published through December 2022 was performed. Included studies presented self-report measures of anxiety at two points across the camp session using a valid and reliable instrument. Meta-analysis was performed using Cohen’s <i>d</i> as an effect size. (2) Mental health was assessed among campers attending an all-boys summer camp through validated self-report questionnaires. Positive and negative mood scores were collected on the first and last full day of camp.</p> Results <p>(1) Eight articles with a sample size of 720 were included for meta-analysis, yielding a statistically significant decrease in anxiety symptoms post-camp compared to pre-camp with a Cohen’s <i>d</i> of −&#xa0;0.25 (95% confidence interval −&#xa0;.37 to −&#xa0;.13; <i>p</i> &lt; .001). (2) Among 464 participants (mean age 13.1&#xa0;years), boys experienced increases (<i>p</i> &lt; .05), across their 2-week camp stay, in Positive Emotion, Homesickness, and Self-Confidence along with a non-significant decrease in Negative Emotion (<i>p</i> = .61).</p> Conclusions <p>Participation in overnight summer camps may have benefits in anxiety levels in youth and promote positive mood and self-confidence. While such camps are promising milieus for population-wide treatment of anxiety and depression in children and adolescents and could represent a cost-effective alternative to outpatient mental health care, additional research is needed to clarify iatrogenic effects and mechanisms of these benefits with formal fidelity monitoring and expanded outreach.</p>