Background Childhood disruptive behaviors are highly prevalent and associated with adverse long-term social and economic outcomes. Trajectories of welfare receipt in early adulthood and the association of childhood behaviors with high welfare receipt trajectories have not been examined. Methods Boys (n = 1000) from low socioeconomic backgrounds were assessed by kindergarten teachers for inattention, hyperactivity, aggression, opposition, and prosociality, and prospectively followed up for 30 years. We used group-base trajectory modeling to estimate trajectories of welfare receipt from age 19–36 years using government tax return records, then examined the association between teacher-rated behaviors and trajectory group membership using mixed effects multinomial regression models. Results Three trajectories of welfare receipt were identified: low (70.8%), declining (19.9%), and chronic (9.3%). The mean annual personal employment earnings (US$) for the three groups at age 35/36 years was $36 500 (s.d. = $24 000), $15 600 (s.d. = $16 275), and $1700 (s.d. = $4800), respectively. Relative to the low welfare receipt group, a unit increase in inattention (mean = 2.64; s.d. = 2.32, range = 0–8) at age 6 was associated with an increased risk of being in the chronic group (relative risk ratio; RRR = 1.16, 95% CI 1.03–1.31) and in the declining group (RRR = 1.13, 95% CI 1.03–1.23), after adjustment for child IQ and family adversity, and independent of other behaviors. Family adversity was more strongly associated with trajectories of welfare receipt than any behavior. Conclusions Boys from disadvantaged backgrounds exhibiting high inattention in kindergarten are at elevated risk of chronic welfare receipt during adulthood. Screening and support for inattentive behaviors beginning in kindergarten could have long-term social and economic benefits for individuals and society.