The measurement of automatic attitudes towards sleep, in addition to reflective self-reports, might improve our ability to predict and explain sleep-hindering practices. Two types of implicit association tests (IATs), a sleep-related evaluations IAT and a sleep-related self-identity IAT, were developed to evaluate their efficacy for assessing automatic sleep-related attitudes. In addition, a speeded self-report measure of sleep evaluations was explored as a means to assess automatic sleep-related attitudes. The study included 136 young adults (age = 21.70 ± 2.22, 43% female). At baseline, the two IATs, the speeded self-report, and standard self-reports of sleep determinants (reflective attitudes, self-efficacy, intention and action planning for sleep-promoting behaviour), sleep hygiene practices, sleep quality, and sleep duration were assessed. All variables except for the sleep determinants were assessed again at 2-week follow-up. The results demonstrated good reliability of the two IAT versions, but both IATs were unrelated to the speeded self-report, the sleep determinants, sleep practices, sleep quality or sleep duration. The speeded self-report correlated significantly with the standard self-reports of sleep determinants. Baseline scores on the IATs or speeded self-report did not predict sleep hygiene practices, sleep duration or sleep quality at follow-up. The findings indicate that sleep-related IATs might not be suited to assess automatic sleep-related attitudes. Further investigation is needed to determine whether speeded self-reports are valid measures of automatic attitudes. Moreover, more empirical research is required to clarify the role of automatic processes for sleep hygiene behaviours.