Poverty is known to be associated with poorer child mental wellbeing. Relatedly, the security and quality of employment are reported to affect adult wellbeing. Less is known about how both poverty and parental employment affect children's mental wellbeing. This paper uses nine waves (2005/06–2017/18) of the Growing Up in Scotland (GUS) study to examine how the longitudinal trajectories of poverty and work intensity are associated with the longitudinal trajectories of mental wellbeing in a nationally representative sample of 3994 children (ages 0 to 12). This analysis was conducted via a bivariate multilevel non-linear growth curve model for the widely used Strengths and Difficulties Questionnaire (SDQ) subscales of conduct problems and emotional symptoms. Results show that unstable work intensity and poverty trajectories arising from the 2008 financial crisis are associated with substantial changes in the trajectories of conduct and emotional problems, but with key differences between the individual outcomes: increasing work intensity is associated with around a fifth of a standard deviation increase in conduct problems; decreasing work intensity over time is associated with around a fifth of a standard deviation increase in emotional problems; material deprivation is associated with an increase in both conduct and emotional problems, at around a tenth of a standard deviation; and longitudinal income poverty trajectories are associated with up to around a fifth of a standard deviation increase in conduct problems, but not emotional symptoms. These findings are discussed with the purpose of informing policies to tackle the effects of unstable and/or changing socioeconomic circumstances on children's mental health wellbeing in the context of an economic crisis, as well as its implications for the contemporary socioeconomic landscape and the devastating effects expected of the COVID-19 crisis.