Transportation-disadvantaged populations often face significant challenges in meeting their basic travel needs. Microtransit, a technology-enabled transit mobility solution, can potentially address these issues by providing on-demand, affordable, and flexible services. However, the extent to which microtransit serves underserved populations and the factors influencing their adoption remain unclear. This research focuses on SmaRT Ride, a microtransit pilot program operated by the Sacramento Regional Transit (SacRT) in the Sacramento area. From early February to the end of May 2024, online and intercept surveys were conducted among underserved populations to understand their travel behavior. After data cleaning, 180 valid responses were collected. Descriptive analysis of the data shows that SmaRT Ride has significantly improved transportation access for these communities. Furthermore, logistic regressions were employed to explore factors influencing the willingness to adopt microtransit and differences cross microtransit users versus non-users with microtransit awareness. Results show that perceived usefulness, the extent to which an individual lacks transportation options, families with children under 18 benefiting from free transit services, and familiarity with ride-sharing services correlate positively to high intention to adopt microtransit; whereas the perceived high mental effort of using it works as a barrier and frequent light rail users are less inclined to adopt microtransit. For underserved individuals who are aware of microtransit, their homeownership, employment status, frequency of using public transit services, and attitude towards transit significantly affect actual microtransit use. This study contributes to the literature by examining a broad range of factors influencing microtransit use and adoption among underserved populations through original survey data. However, it is limited by its cross-sectional design and small dataset.