For the timely treatment and management of depression, a high level of depression literacy (DL) is needed. This study aimed to examine the level of DL and factors associated with DL among middle-aged Korean adults and to verify the relationship between DL, depression, and quality of life (QoL). This cross-sectional study included 485 participants aged 40 to 64 years recruited from five provinces in Korea. DL was measured using a 22-item questionnaire and analyzed by multiple linear regression and correlation analysis. The DL level of the participants was moderate and the correct answer rate was 58.6%. In particular, non-pharmacological treatments, differential symptoms, and pharmacological treatments were low. Out of the participants, 25.2% had depression, and the difference in DL between those with and without depression was not statistically significant. The positive factors associated with DL were being female, having higher education, and being employed. DL was not correlated with depression or psychological QoL. However, higher DL was associated with less heavy drinking, normal body mass index, and not smoking. Improving DL can help individuals seek timely professional help and reduce mental health disparities. Further studies should continue to investigate and develop the association between DL and health-related behaviors as well as depression and QoL to effectively treat and manage depression.