Attributional (explanatory) thinking involves the appraisal of factors that contribute to performance and is instrumental to motivation and goal striving. Little is understood, however, concerning attributional thinking when multiple causes are involved in the transition to new achievement settings. Our study examined such complex attributional thinking in the transition from high school to university, a shift from familiar to novel learning environments, in the context of Weiner's attribution theory (1972, 1985, 1995, 2006). At the start of the academic year, students rated the extent to which each of six common attributions contributed to poor performance to ascertain their relative importance to each other. A fixed order of attributions was reported as contributing to poor performance that was identical across five independent cohorts of first-year students (effort, test difficulty, strategy, professor quality, ability, luck, respectively). Cluster analysis revealed that students differed in combining these attributions into clusters suggesting diminished or enhanced control over poor performance. These differences in attribution clusters were associated with cognitive and affective outcomes at the start of Term 1, and with course grades and GPA at the end of Term 2. Student differences in complex attributional thinking are discussed in terms of transitions to new achievement settings. (Contains 1 figure and 4 tables.)