The buffering effects of supervisor support on the stressor–strain relationship have proven elusive in prior research (Beehr, Farmer, Glazer, Gudanowski and Nair (2003), ‘The Enigma of Social Support and Occupational Stress: Source Congruence and Gender Role Effects,’ Journal of Occupational and Health Psychology, 8, 220–231). We built on emerging work on source congruence and conservation of resource theory to test a series of hypotheses intended to clarify these mixed findings. Using a sample of 768 employees from 45 organizations in North America, results from moderated regression analyses, showed that the effects of supervisor support on the stressor–strain relationship depended on source congruence. In accordance with our predictions, although we found buffering effects for the physical stressors–strain relationship, we found a reverse buffering effect for the role conflict–strain relationship. These differential buffering effects did not emerge when considering coworker support. We discuss the implications of our results for shedding light on the mixed evidence regarding buffering work stressors reported in prior research.