Research on multitasking during travel has increased, yet most studies have focused on public transit passengers. This work investigated travel-based multitasking and its potential determinants across multiple travel modes (automobile, nonmotorized, and transit) using a 2016 survey of around 650 commuters in the Portland, Oregon, region. First, exploratory factor analysis on 23 activities yielded two activity groups: those related to information and communications technologies (texting/emailing/messaging, reading electronically, and using social websites/apps) and those that are more passive in nature (viewing scenery or people watching and thinking/daydreaming). Next, mode-specific binary logit models predicted participation in each activity (or activity group) as a function of travel time, traveler socio-demographics, perceptions, and other factors. Travelers using riding modes (transit riders and auto passengers) engaged in a greater number and variety of activities, while vehicle (auto and bicycle) operators did fewer and more passive activities. For walking/bicycling commuters, exercising or being physically active appeared to be an enjoyable and productive use of travel time. On the other hand, many instances of travel-based multitasking for transit passengers may be more about coping with a burdensome or boring commute or the result of being time poor. These findings offer important implications for understanding motivations for travel-based multitasking, sustainable transportation mode choices, and future demands for autonomous vehicles.