To understand the relationship between employee performance and abusive reactions from supervisors, we examine the role of supervisors' attributions about employees' performance. Drawing on the fundamental attribution error, we argue that supervisors over-attribute lower levels of performance to employees' internal factors (i.e., conscientiousness), which then triggers higher levels of abusive supervision. In Study 1, we collected data from 189 supervisor-employee dyads. The results indicated that lower levels of supervisor-rated employee performance related to supervisor biased attributions to employee conscientiousness, which in turn resulted in employee-rated abusive supervision. In Study 2, we combined a recall task with a vignette design to replicate and extend our findings. We demonstrated that after adjusting for the baseline level of employee conscientiousness, supervisors over-attributed poor performance to employee conscientiousness and then engaged in higher levels of abusive behaviors. Further, consistent with premises of fundamental attribution error, we found that in the absence of information about who was at fault for poor performance, supervisors over-attributed poor performance to internal factors (employee) as compared to external factors (software malfunction). Taken together, our findings demonstrate that biased attributions about employee conscientiousness help explain the relationship between employee performance and abusive supervision.