There is instability in the developmental course of problem gambling [PG] over time; however, studies that examine PG at an aggregate level obscure these variations. The current study employed data from a longitudinal study of Australian young adults to investigate: 1) PG patterns (i.e., resistance, persistence, desistence, and new incidence); 2) prospective risk and protective factors for these patterns; and 3) behavioural outcomes associated with these patterns. A sample of 2261 young adults (55.73% female) from Victoria, Australia, who were part of the International Youth Development Study completed a survey in 2010 (T1, age 21) and 2012 (T2, age 23) measuring PG (two items based on established measures), risk and protective factors, and behavioural outcomes. The majority of the sample (91.69%) were resistors (no PG at T1 and T2), 3.62% were new incidence PG cases, 2.63% were desistors (PG at T1 but not T2), and 2.07% reported persistent PG at T1 and T2. Individual civic activism was protective of new incidence PG, while affiliation with antisocial peers and frequent alcohol use increased the risk of persistence. Persistent problem gamblers also experienced the greatest number of poor behavioural outcomes at T2. New incidence was associated with internalising symptoms at T2, while desistance was not associated with any behavioural outcomes. In conclusion, each PG pattern was associated with different predictors and outcomes, highlighting the need to consider variation in the course of young adult PG in order to provide efficacious prevention and intervention approaches, and to protect against relapse.