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Though urban-associated shifts in behavior of adult animals are well documented in the literature, few studies have investigated how urbanization shapes juvenile behavior. For birds, the transition from nestling to fledgling (i.e., leaving the nest or fledging) marks a critical transition that profoundly affects survival. Though species often fledge at different times during the day, young birds are thought to time their fledging relative to civil dawn—which may mark when habitats are first visible for birds. Because sensory pollution within cities can affect the timing of daily activities, we hypothesized that urbanization and light pollution (artificial light at night (ALAN), in particular) would promote earlier fledging times. To test this hypothesis, we examined whether urbanization and light pollution were associated with shifts in diel patterns of fledging in Northern Cardinals (Cardinalis cardinalis) breeding across a rural-to-urban gradient in central-Ohio, USA. From 2007 to 2010, we deployed nest cameras across 227 nests and documented 72 fledging events, from which we characterized and compared diel patterns of fledging between urban and rural cardinals. Consistent with our hypothesis, fledging times were ~ 23% earlier in urban cardinals (5.49 ± 0.63 SE h after civil dawn) compared to their rural counterparts (7.13 ± 0.62 SE h), and cardinals fledged progressively earlier as the landscape became more urbanized and light-polluted. Our findings suggest that ALAN is among many urban-associated factors (e.g., changes in predator communities, predation risk) that may shape juvenile behavior, but future studies are required to identify the mechanisms underlying this shift in fledging behavior. [ABSTRACT FROM AUTHOR]