This mixed-methods study combines experience sampling and smartphone log data to explore momentary associations between passively sensed smartphone use, feeling rushed, and perceived task juggling in daily life. Using data from 774 adults, we analyze how four use features (frequency, duration, fragmentation, and notifications received) of four mobile app categories (email, social media, chat, and work communication) affect how rushed people feel, both directly and indirectly by increasing their perceived juggling load. At the between-person level, persons who use work communication apps more frequently and longer, and who receive more chat notifications, also felt more rushed on average. Findings also revealed within-person associations in the theorized direction (e.g., increased email frequency predicting increased task load and feelings of being rushed) for nearly all features of three out of four examined app categories, with social media use features as a noticeable exception. Perceived task juggling mediated these associations, suggesting that the examined smartphone use features contribute to feeling rushed by increasing the (real or perceived) load of tasks that people juggle within and across role domains. Some patterns differed based on age, gender, parenthood, and segmentation preference. Taken together, these findings support the theoretical link between technology use and experiences of time scarcity.