BackgroundPlacement stability is tied to well-being among children living in foster care, yet residential mobility remains largely unexplored for transition-age youth residing in extended foster care (EFC) between ages 18 and 21. During the time young adults in EFC can remain in foster homes, child welfare agencies offer living arrangements tailored to the transition into adulthood. In supervised independent living placements (SILPs), residents receive monthly stipends to cover their housing expenses and are responsible for covering food, utilities, and other basic needs-related costs. Transitional housing placements (THPs) offer light-touch caregiving during the transition to independence to ensure that residents have their basic needs met. ObjectiveThe current study is the first comprehensive examination of factors associated with residential mobility in a statewide population of young adults residing in EFC. ParticipantsUsing California administrative Child Protective Services records, we identified young adults who turned 18 between 2016 and 2019 and lived in care for at least 1 week (N = 10,517). MethodsNegative binomial regression evaluated the association between residential characteristics and per-year EFC moves. ResultsWe found that young adults had a median number of 1.0 moves during EFC, with a median rate of 0.67 moves per year in EFC (i.e. roughly one move every 18 months). SILPs and THPs were the most common primary residence types among the study population (41.6 % and 26.0 %, respectively). The average duration of stay in EFC was two years, which varied by primary residence type. Regression results showed that predominant residence type in EFC was associated with EFC mobility, with young adults in SILPs being more likely to experience slightly higher mobility than those primarily living in other residence types (0.82 versus 0.75 moves per year in EFC). ConclusionsFindings suggest that housing for EFC residents tends to be long-lasting and relatively stable in California. Modest variations in mobility by residential type and by experiences in foster care before age 18 underscore the importance of integrating housing and psychosocial resources during independent living planning processes. The commonality of out-of-county residence should be considered when determining housing and transportation expenses for residents, given its potential implications for access to medical and behavioral health care, academic institutions, and employment opportunities for young adults receiving EFC services.