This study examines several factors that affecting user's behavioral intention to use GRAB, one of the most popular online transportation services in indonesia. The proposed model uses several popular IT adoption theories such as TAM, TPB, and DOI and select nine factors to be investigated furtherly. A research model is developed and empirically tested by using structural equation modeling on datasets consisting of 992 GRAB users in indonesia. This study finds that the factors of internal perception (petceived uefulness and perceived ease of use) and innovation characteristic (compability) have impacts on users' behavioral intention to use online transportation service in indonesia.