Parenthood is one of the most important social roles, but the consequences of becoming a parent are not always as expected. It is estimated that in developed countries, up to 5%–14% of parents regret their decision to have children and if they could turn back time, they would choose childlessness. While such a situation can have serious consequences for the entire family system, our knowledge of the causes and consequences of regretting parenthood is very limited. Beyond the possible taboo, one factor that is certainly responsible for the small number of studies on regretting parenthood is the lack of questionnaires to measure its severity. In the present study, we decided to fill this gap and developed a new questionnaire—the Parenthood Regret Scale. In a series of three studies (total N = 2,994) conducted on English-speaking, French-speaking, and Polish-speaking samples, we analyzed the factor structure, reliability, and validity of the new scale. The results confirmed that the Parenthood Regret Scale has a single-factor structure, which has been replicated in the three languages. Furthermore, the analyses confirmed that higher parenthood regret is negatively related to life satisfaction, and positively related to the severity of depressive symptoms and parental burnout. In light of the results obtained, it can be concluded that the Parenthood Regret Scale is a valid and reliable measure that can help advance research on an almost unknown issue of great social importance.