Evidence demonstrates that health professionals have limited knowledge about childhood sleep, frequently do not screen for these problems and often rely on parents to raise sleep issues at clinic visits. However, little is known about parents’ sleep knowledge. The goal of this study was to assess parents’ knowledge of sleep and specifically: (i) sleep aspects related to the age of children; (ii) developmentally normal sleep; and (iii) sleep problems that may lead to parents’ ability to raise sleep issues at clinic visits. This study evaluated the knowledge of 170 parents of children aged 2–17 years about infant, child and adolescent sleep patterns and problems. The majority of parents could not answer correctly questions about developmental sleep patterns or sleep problems, but were more likely to answer correctly questions about normal infant sleep patterns and about sleep problems during waking hours. Parents also were more likely to answer ‘don’t know’ to questions about: (i) older children and adolescents; (ii) sleep apnea; and (iii) dreams and nightmares. The implications of these findings for the identification, intervention and prevention of childhood sleep problems are discussed.