In Study 1, we tested a model in which two job demands (i.e., changes in tasks and ambiguities about work) and organizational resources (i.e., interpersonal and informational justice) influence work engagement through the satisfaction of individuals’ psychological needs for autonomy, competence, and relatedness. In Study 2, we examined the indirect effects of the same job demands and organizational resources on burnout through need thwarting. We also examined the mediating role of organizational resources in the relationships of changes in tasks and ambiguities about work to need satisfaction (Study 1) and need thwarting (Study 2). Structural equation modeling performed on cross–sectional data collected from 461 workers in Study 1 and 708 employees in Study 2 provided support for the hypothesized models. Specifically, results revealed that changes in tasks and ambiguities about work have direct and indirect effects (via organizational resources) on psychological need satisfaction and need thwarting, which in turn positively predicted work engagement and burnout, respectively (p < .05). Research implications and study limitations are discussed.