Pretreatment is an essential technique for enhancing the efficiency of extraction. Among many types of pretreatment processes, freezing and drying have been recognized as the thermophysical pretreatment techniques that can be applied to many solid samples before being subjected to extractions. However, the effectiveness of the pretreatment conditions highly dependent on the type of raw materials. Therefore, this study aimed to investigate the effect of pretreatments on the extraction of essential oil through hydro- distillation. Kaffir lime leaves was selected as the studied raw material because it is cheap and populary used as an ingredient in various products. Pretreatment conditions such as air drying and freezing of the kaffiir lime leave before being subjected to hydro- distillation of essential oil was conducted in this study. Compared to fresh samples, it is found that freezing and air drying of kaffir lime leaves resulted in different essential oil accumulation rates, extraction yields of essential oil, and extracted volatile compounds. The dried sample provided the highest essential oil yield ( 3.7 %) with a shorter extraction time of about 60 min compared to the frozen sample (1.5 % of essential oil yield and about 90 min of extraction time). The fresh sample resulted in the lowest essential oils yield (1.4 %) with a longer extraction time of about 150 min. Furthermore, (GC-MS) results revealed that the main volatile compounds in essential oils extracted from kaffir lime leave are citronellal (69.9 – 71.1 %), citronellol (6.6 – 9.2 %), and linalool (5.6 – 6.7 %). The contents of volatile compounds in essential oils are affected by pretreatment techniques.. This finding can be very useful data for the extraction of essential oil from Kaffir lime leaves with better quality and yield by hydro-distillation.