Teacher collaboration and social-emotional learning (SEL) are extant school improvement strategies intended to have a positive effect on student learning outcomes. The purpose of this quantitative, "ex post facto" study was to examine possible correlations between degree of teacher collaboration and use of instructional practices that support student SEL among lower secondary teachers (grades 7-9) in the United States (Leonard, 2021). Correlational analyses were conducted using a secondary dataset of the 2018 Teaching and Learning International Survey (TALIS) sponsored by the Office of Economic Cooperation and Development (OECD, 2018). Results showed strong, statistically significant relationships between frequency of teacher engagement in higher-intensity "student-facing" collaborative actions such as peer observation, and the enactment of instructional approaches that contribute to student SEL, such as helping students believe they can do well in school and having them work in groups to come up with a joint solution to a problem. Implications for research and for the advancement of teacher collaboration and SEL in P12 schools are discussed.