Water deer (Hydropotes inermis) are classified as “Vulnerable” on the IUCN Red List due to their declining population trend, indicating global concern. However, water deer are considered a harmful species in South Korea where the population is relatively abundant. The population status of water deer varies across their geographical range, but information on their distribution is limited due to insufficient research and reporting. This study, therefore, aimed to identify the environmental variables influencing the distribution of water deer and to provide insights into their daily behavior patterns. Camera traps were deployed at 108 points within 22 grid cells (each 5 km × 5 km), from March to September 2021, located in the central-east part of the Korean Peninsula. Water deer were detected 92 times across 17 grid cells. A single-season occupancy model revealed that occupancy decreases with the increase in normalized difference vegetation index (NDVI) (β_NDVI: -1.00±0.21), which is presumed to be related to the use of forbs or low woody plants as food resources. Detection was influenced by slope, with higher slopes likely limiting mobility and, thereby reducing detection (β_slope: -0.60±0.03). The diurnal behavior patterns were confirmed to be crepuscular, with activity primarily around sunrise and sunset. These findings are expected to enhance the understanding of this species and may be used for the management of water deer as a problematic species in South Korea, as well as for species conservation efforts internationally.