Background: Play is essential for child growth and development, and may have academic and social-emotional implications. To understand the relationship between in-school play opportunities and academic achievement (AA) and social-emotional well-being among elementary school students, a systematic review of the current in-school play literature was conducted. Methods: Keywords were input across 7 search engines. After screening, 20 peer-reviewed publications related to play, AA, and social-emotional well-being met the inclusion criteria for this review. Findings: Across the included publications, recess was the only in-school play opportunity assessed. Overall, student behavior and social-emotional outcomes benefited from more recess while mixed results were found between recess participation and academic outcomes. However, more recess was not detrimental to AA. Conclusion: The findings from this review support the need for recess as part of a whole child approach to education that may mitigate the negative outcomes of sitting through long periods of instruction. More research is needed on the AA and social-emotional effects of other types of in-school play opportunities (ie, centers, play stations, and other breaks). Findings from this review indicate that recess is a necessary part of the elementary school day.