Mental diseases and pain are serious public health problems and are a leading cause of disability worldwide. The aim of this study is to describe how pain and psychological distress separately and in combination are associated with four income trajectories over nine years in a cohort of long-term social assistance recipients (LTRs). A cohort of 456 LTRs from 14 municipalities in Norway were divided into four groups based on the presence or absence of pain and/or psychological distress. These were surveyed in 2005, and later linked by personal identification numbers to high-quality longitudinal administrative data covering the period 2005–2013. Methods include calculation of income statuses based on main sources of income, and multinomial logistic regression analysis. In the group without pain and psychological distress, earnings from work as main source of income (14.6–38.0%) and disability benefits (2.9–16.1%) increased over the period. In the ‘double burden’ group the proportions who had social assistance as main income decreased (68.2–21.5%) and the proportions with disability benefits increased over time (5.6–36.6%). Only 27.2% of the total sample had earnings from work as their main income in 2013. LTRs are extra burdened by pain and psychological distress, and this has consequences for their life opportunities and income trajectories. This study indicates that the primary goal of the social assistance system, to make the clients self-sufficient, is hard to achieve. A better co-operation between health services and work-related services is needed.