The effects of over-qualification (OQ) are becoming more established, yet little is known about the processes which drive these outcomes, or why outcomes are sometimes positive rather than negative. Less is known about different forms of over-qualification, whether they exist, and, whether they make a difference to such outcomes. Drawing on the theory of needs-supplies fit, the current research examined how two distinct forms of over-qualification (intentional and unintentional) relate to life satisfaction, job satisfaction, organisational commitment, turnover intentions, and job performance. Data were collected by means of an online self-report survey. Two hundred and twenty-seven respondents (61% female, 39% male) provided data at one time point. Two distinct forms of over-qualification emerged. Ninety participants were intentionally over-qualified and predominantly chose jobs below their qualifications due to work-life balance considerations (e.g., wanting more time for educational pursuits, family, hobbies, and leisure activities). Eighty-four participants were unintentionally over-qualified (i.e., not over-qualified by choice), and fifty-three participants were not over-qualified. Women reported choosing jobs below their qualifications significantly more often than men, as did individuals below the age of 30 years. Unintentional over-qualification proved to be a more harmful form of over-qualification and was linked to a range of undesirable outcomes. Over-qualified employees should not be mass categorised as they have been in many previous studies. Although unintentional over-qualification should be avoided, the same cannot be said for intentional over-qualification. Over-qualified individuals who choose their employment situation appear to represent a largely unrecognised, underutilised, and potentially valuable resource for organisations.