Pregnant women are at higher risk of transmitting the infections to their foetus. This prompted the “Prevention of Mother to Child Transmission (PMTCT) Program” in Malaysia since 1998. The objective of this cross sectional study was to determine the knowledge, attitude and practice (KAP) of pregnant mothers in the west of Sabah towards HIV/AIDS and its influencing factors. Data were obtained through self administered questionnaires. Results showed that only 32.2% of the respondents have good knowledge compared to 67.8% who had poor knowledge (p <0.001) of HIV/AIDS. Majority of them (56.4%) have good attitude and practice towards HIV/AIDS compared to the remaining poor attitude and practice respondent (44.4%) (p<0.001). Radio/TV (90.2%) and reading materials (83.9%) were the main sources of obtaining information. Main influencing factors for having good knowledge towards HIV/AIDS were women aged < 30 years old, have high education, who perceived on having good knowledge towards HIV/AIDS and received health education from health staffs. Mean while, influencing factors for having good attitude and practice towards HIV/AIDS were women having high education and received health education from health staffs. Therefore, implementation of PMCTC must be reviewed regularly to ensure the program reach its targets.