<p>Mobility as a Service (MaaS) is a platform which integrates transport services and allows people to make trip planning, booking, and payment through a single application. Previous studies mainly concentrate on understanding bundle (a subscription plan offering a combination of transport services for a fixed price over a certain period) design, and bundle choice behaviour while few explore the spatio-temporal dynamics of public transport ridership before and after the introduction of MaaS. A MaaS trial (ODIN PASS) in Brisbane, Australia, targeting the University of Queensland students and staff, was launched at the end of July 2021. The trip booking data of this MaaS trial includes public transport records for 5300 participants, and 264 of them agreed to share their public transit smart card data as part of the research. Through employing the flow-comap technique, this study aims to explore when and where the changes in public transport ridership occurred after the launch of a MaaS trial by using both the trip booking data and public transit smart card data. Results reveal that public transport ridership in suburban areas increases after the introduction of MaaS. An ordinary least squares regression is also employed to examine the extent to which trip characteristics, built environment factors, and socio-economic indexes influence the relative change in average public transport ridership at the individual level across five-time intervals (holiday, am peak, mid-day, pm peak, and night). Our findings guide transport planners to identify when and where public transport ridership increases due to the introduction of MaaS. This information can be used to improve public transport accessibility and facilities to meet the increasing ridership.</p>