In a series of 4 studies we investigated the relations of mastery goal structure and 4 dimensions of the classroom social climate (teacher academic support, teacher emotional support, classroom mutual respect, task-related interaction). We conducted multidimensional scaling with separate adolescent samples that differed considerably (i.e., by racial and demographic characteristics, grade level, and educational contexts). Studies 1, 2, and 3 (Ns = 537, 537, and 736, respectively) showed that mastery goal structure items occupied a central space among the climate items and overlapped partially with the areas formed by the respect and academic and emotional support items. In Study 4 (N = 789) we investigated the structural relations of mastery goal structure and the 4 social climate scales with another adolescent sample. Using confirmatory factor analysis we compared these 2 models: (a) all 5 measures at the same level and (b) mastery goal structure as a 2nd-order factor, with the 4 social climate measures as its indicators. The fit for both models was good, although the 1st-order model fit was better. Nevertheless, in the 2nd-order model mastery goal structure accounted for between 92% and 67% of the variance in the climate measures. (Contains 1 footnote, 3 tables, and 4 figures.)