Abstract Although leaders in organizations may set stretch goals (i.e., extremely difficult goals that seem unattainable given employees' current capabilities) to motivate employee development, the extreme difficulty of such goals may also demotivate them. Understanding when stretch goals may foster rather than hinder employee development is critical. By exploring the contingent role of leader goal support, this research delves into the motivational and demotivational effects of stretch goals. The results of an experimental study and a multi‐wave field study suggest that employees are more likely to appraise stretch goals as challenges when leader goal support is higher, and more likely to appraise stretch goals as hindrances when leader goal support is lower. Challenge and hindrance appraisals, subsequently, lead to proactive skill development and withdrawal behaviour, respectively. That stretch goals were more directly related to hindrance than challenge appraisals in both studies should caution leaders in organizations against using stretch goals often. When stretch goals are used, they should be complemented with high leader goal support.