Virtually all studies on workaholism and engagement rely on self-report questionnaires. However, the limitations of self-reports are widely acknowledged and potentially peer ratings may overcome these imitations. Using a sample of 73 dyads composed of focal workers and their colleagues, the present study aimed: (1) to compare focal workers’ and coworkers’ perceptions of work engagement and workaholism; and (2) to explore the discriminant validity of engagement and workaholism. Our results showed a considerable agreement between both raters (i.e., focal workers and coworkers) in levels of engagement and workaholism. In contrast to previous findings, a significant difference between raters on the cognitive dimension of workaholism (i.e., working compulsively) was observed. In sum, our results provided further evidence for the discriminant validity between the two forms of heavy work investment (download full article).