Grit (effortful persistence) has received considerable attention as a personality trait relevant for success and performance. However, critics have questioned grit's construct validity and criterion validity. Here we report on two studies that contribute to the debate surrounding the grit construct. Study 1 (N = 6,230) examined the psychometric properties of a five-item grit scale, covering mainly the perseverance facet, in a large and representative sample of German adults. Moreover, it investigated the distribution of grit across sociodemographic subgroups (age groups, genders, educational strata, employment statuses). Multiple-group measurement models demonstrated that grit showed full metric, but only partial scalar, invariance across all sociodemographic subgroups. Sociodemographic differences in the levels of grit emerged for age, education, and employment status but were generally small. Study 2 investigated how grit relates to career success (income, job prestige, job satisfaction) and career engagement (working overtime, participation in continuing professional development courses, attitudes toward lifelong learning) in an employed subsample (n = 2,246). When modeled as a first-order factor, grit was incrementally associated with all indicators of career success and especially of career engagement (.08 ≤ β ≤ .75)-over and above cognitive ability and sociodemographic characteristics. When modeled as a residual facet of conscientiousness, grit largely retained its criterion validity for success but only partly for engagement (-.14 ≤ β ≤ .61). Our findings offer qualified support for the psychometric quality of the short grit scale and suggest that grit may provide some added value in predicting career outcomes. We critically discuss these findings while highlighting that grit hardly differs from established facets of conscientiousness such as industriousness/perseverance.