Competition in the transportation services business is currently growing rapidly and advancing. Many companies in similar fields have sprung up so as to make competition in getting and keeping customers increasingly tight. In order to survive in the circle of competition, companies must have the ability to provide the best quality of service in order to increase customer satisfaction. This study aims to examine the effect of transportation service quality on passenger satisfaction. The study population was all passengers or users of the UMY fleet bus services. The sample in this study amounted to 70 people. Data collection instruments using a questionnaire that was assessed with a Likert scale, each of which has been tested and has met the requirements of validity and reliability. Data analysis uses multiple linear regression, hypothesis testing, and Servqual calculations to determine the value of GAP and then Importance-Performance Analysis (IPA) to find the 2 attributes that must be considered in the Cartesian diagram. The results of multiple linear analyzes show that service quality consisting of five variables: reliability, responsiveness, assurance, empathy, and tangibles have a positive and significant effect on passenger satisfaction. While the results of the analysis using the importance performance analysis (IPA) method show that the five variables used are still not in line with the expectations of passengers and need for improvement in service quality in order to increase passenger satisfaction.