Background: Inflammatory markers, such as C-reactive protein (CRP), have been shown to be socially patterned in older age groups and are hypothesized as mediating pathways between socio-economic position (SEP) and cardiovascular disease. However, it is unclear when socio-economic differences in CRP emerge across the lifespan. To investigate this, income-related inequalities in CRP across all ages were explored. Methods: Data from 8,799 participants (aged 16+) of wave 2 (1/2010-3/2012) Understanding Society (UKHLS) were employed. Disadvantaged SEP is defined as belonging to the lowest quartile of equivalised household income. Regression models estimated quadratic interactions of age with SEP to explore CRP-age trajectories for disadvantaged and less disadvantaged SEP; lifestyle indicators (smoking, physical activity and body mass index) were added to models, along with gender and ethnicity. First, raw income-related inequalities in CRP were estimated across age. Subsequently, the pertinent inequalities were decomposed to estimate the effect attributed to differences in the lifestyle indicators between income groups across ages. Results: Income-related inequalities in CRP emerge around the age of 30 after which they non-monotonically increase to the age of 55, where they peak, and then slightly reduce and remain constant until 70s; subsequently, they further narrow, converging at older ages most likely due to healthy survivor effects. Decomposition analysis shows that the proportion of the raw inequalities attributed to differences in lifestyle-related factors is lower in middle ages and higher in younger and older individuals (between 17 to 88%). CRP inequalities still remain; however they are reduced in magnitude and restricted to 40-75 age range, while peaking at the same age (55 to 60). Conclusions: Income-related CRP inequalities emerge in 30s and do not follow homogenous patterns across age. These inequalities remain apparent when considering lifestyle related factors but the proportion of the inequalities explained varies by age, which requires further investigation.