To help alleviate the widespread health problem created by poor sleep, health organizations invest considerable resources into public sleep education. Yet there is limited research to support the notion that sleep education leads to better sleep quality, whether for poor sleepers or the general population. The present study examined the relationships between sleep knowledge, sleep practice and sleep quality in a sample of 946 participants (mean age = 38.5 years, SD = 14.4, 67% women), 394 of whom were identified as poor sleepers (mean age = 41.4 years, SD = 15.2, 58% women). An online questionnaire was used to cross-sectionally test these relationships for the poor sleepers, as well as the entire sample. Sleep knowledge was significantly related to sleep practice for the entire sample, but not for the poor sleepers. However, significant moderate relationships between sleep practice and sleep quality were found for both poor sleepers and the entire sample. Further analysis showed that sleep practice mediated the relationship between sleep knowledge and sleep quality for the entire sample. However, when other factors known to affect sleep quality (e.g. age and gender) were controlled, there was no significant relationship between knowledge and sleep quality. These results indicate that current sleep education may not be effective in improving sleep quality, particularly for poor sleepers. Further research into additional factors (e.g. dysfunctional beliefs) influencing sleep quality, and the implementation of accurate sleep knowledge are needed.