In comparison to their public and for‐profit counterparts, not‐for‐profit employees report experiencing higher work demands. Despite the harmful effects attributed to this important sector difference, few, if any, empirical studies in the not‐for‐profit literature have investigated how job‐related resources, such as control over one's job, help buffer work demands' strain‐inducing impact. The present study fills this important gap in the extant not‐for‐profit literature by testing a recently introduced nonlinear stressor‐strain model on a sample of 363 employees from two different types of not‐for‐profit human service agencies located in the city of New York. As hypothesized, the nonlinear demand by linear control interaction term was statistically and significantly associated with job strain in the predicted direction. Study data not only challenge the linear nature of Karasek's seminal demand‐control model, but are also the first to uncover this unique finding in a sample of not‐for‐profit human service employees. Implications for practice and theory are also discussed.