Relationships among self-construal, self-efficacy, and group behaviors during a group problem-solving task with friends and acquaintances were hypothesized. The sample comprised 126 students in Grades 8-11, from 5 randomly selected government high schools, organized into 42 groups. Data collection involved self-reports and observations. Self-report data measured self-construal, self-efficacy for working with friends, and self-efficacy for working with acquaintances, and the observational data captured salient student behaviors. Data were analyzed using exploratory factor analysis and multilevel modeling. Self-efficacy for working with acquaintances was related to the development of ideas and also the critical review of ideas in groups. This study provides insights into the relatively underexplored phenomena of group work with friends and acquaintances.