Millennials are increasingly reported to behave, and travel, differently from previous generations at the same stage in life: They postpone the time they obtain a driver’s license, often live in urban locations and do not own a car, drive less if they own one, and use alternative travel modes more often. However, the reasons behind these trends, and their long-term impacts on the future growth of Californian cities, are still unclear. This study investigates these questions through the analysis of a comprehensive dataset collected in fall 2015, as part of a panel study of millennials’ lifestyles, travel behavior and adoption of new technologies.