The results of two cross-sectional studies (N = 220 and N = 258) indicate that employees' work-related mastery-approach goals (i.e. the striving to improve one's performance at work) were positively associated with work engagement. Further, this relationship is explained by high levels of instrumental support. In contrast, employees' work-related mastery-avoidance goals (i.e. the striving to avoid performing worse than one aspires to) are positive predictors of job detachment and fatigue. The relationships between mastery-avoidance goals and these detrimental work outcomes are explained by low levels of perceived emotional support. Altogether, these results suggest that workers with mastery-approach goals tend to invest in their social work environment by establishing instrumental exchange relationships. Such relationships are considered functional for task performance and explain the positive relationship with work engagement. Employees who hold mastery-avoidance goals, on the other hand, tend to withdraw from the social structure of the workplace which explains the negative relationship with emotional support. In turn, given the lack of emotional support, psychological detachment and fatigue may emerge. These results are discussed in relation to the surging interest in the social mechanisms that result from the pursuit of achievement goals.