Overclaiming questionnaires (OCQs), which capture overclaiming behavior, or exaggerating one's knowledge about a given topic, have been proposed as potentially indicative of faking behaviors that plague self-report assessments in job application settings. The empirical evidence on the efficacy of OCQs in this respect is inconsistent, however. We draw from expectancy theory to reconcile these inconsistencies and identify the conditions under which overclaiming behavior will be most indicative of faking. We propose that the assessment context must be tied to an outcome with high valence, and that the content of the OCQ must match the perceived knowledge requirements of the target job, such that overclaiming knowledge of that content will be instrumental to receiving a job offer. We test these propositions through three studies. First, in a sample of 519 applicants to firefighter positions, we demonstrate that overclaiming on a job-relevant OCQ is positively associated with other indicators of faking and self-presentation. Next, we demonstrate through a repeated-measures experiment (N = 252) that participants in a simulated personnel selection setting overclaim more knowledge on a job-relevant OCQ than on a job-irrelevant OCQ, compared with when they are instructed to respond honestly. Finally, in a novel repeated-measures personnel selection paradigm (N = 259), we observed more overclaiming during a selection assessment compared with a research assessment, and we observed that this job-application overclaiming behavior predicted deviant behavior following selection. Altogether, the results show that overclaiming behavior is most indicative of faking in job application assessments when an OCQ contains job-relevant (rather than job-irrelevant) content. (PsycInfo Database Record (c) 2020 APA, all rights reserved).