This study links idiosyncratic deals (i-deals) to job design theory. It investigates the impact of individually negotiated job changes on performance, self-efficacy, and psychological strain through their intervening effects on work design. Based on a sample of 187 health care professionals employed by a hospital in Germany, three types of work design-related i-deals were investigated: (1) task, (2) career, and (3) flexibility i-deals. Consistent with hypotheses, the three types of i-deal had differential effects on work characteristics, and each in turn related to different outcomes. Specifically, job autonomy mediated the task i-deals—job performance relationship; skill acquisition mediated the career i-deals—occupational self-efficacy relationship; and reduced work overload mediated the flexibility i-deals—emotional and affective irritation relationships. Leader–Member Exchange was confirmed as an antecedent of all three types of i-deals. Task, career, and flexibility i-deals are discussed as ways to make work more intrinsically motivating, ensure one’s professional advancement, and balance workplace stressors.