The aim of this study was to assess the prevalence of toothache, associated factors and impact of this condition on the Child Oral Health Related Quality of Life (COHRQoL) in preschoolers. The study was carried out in Santa Maria, Brazil, during the National Children's Vaccination Day, and 534 children aged 0 to 5 years were included. Clinical variables included dental caries and dental trauma. A questionnaire was responded by the parents and provided information about several socioeconomic indicators, dental service use and toothache. Toothache was collected by the question: "Has your child ever had a toothache - Yes or no?". Data on COHRQoL were assessed using the Brazilian version of the Early Childhood Oral Health Impact Scale (ECOHIS). Multivariable Logistic regression models were performed to assess the association between the predictor variables and outcomes. The prevalence of toothache was 10.11% (95% CI: 7.55% - 12.68%). Older children had a higher chance of presenting dental pain (OR 2.72; 95% CI: 1.01 - 7.56), as well as children with caries experience (OR 3.43; 95% CI: 1.81 - 6.52). Moreover, children who had not visited the dental service in the last 6 months were less likely to present toothache (OR 0.51; 95% CI: 0.28 - 0.95). The presence of dental pain negatively affects the COHRQoL; those with toothache presented a higher chance of having higher impact on the total scores of ECOHIS (OR 4.18; 95% CI: 1.76 - 9.95) than those without toothache. Similar observation was found for the child section of the questionnaire (OR 5.54; 95% CI: 2.15 - 14.24). Toothache negatively affects COHRQoL and is associated with caries experience, age and use of dental service.