Purpose: Safe sleep practices (SSP) are among the main strategies to reduce sleep-related sudden unexplained infant death (SUID). Daycare personnel must be knowledgeable and trained in SSP related to SUID. This study explored the experience, knowledge, and confidence regarding SSP associated with SUID of daycare personnel. Methods: A cross-sectional survey was conducted with 395 staff members at 61 daycare centers to measure their experience related to SSP (10 items), related to sleep position and location, bedding materials, and other topics; knowledge of SSP (18 items); and confidence in SSP (1 item) related to SUID. Results: A substantial proportion (23.6%) of respondents used the lateral or prone positions for infant sleep. On average, 4.5 bedding materials were used for infant sleep. Participants showed a lack of knowledge about SSP as indicated by a 56.6% knowledge of SSP related to SUID correct answer rate. Personnel who received SUID education were more knowledgeable and had more confidence regarding SSP than those who did not. More knowledge and confidence related to SSP were associated with better adherence to SSP. Conclusion: Standard SSP guidelines should be developed based on South Korea's culture of childcare for educating both childcare professionals and parents at home.