Introduction Associations between indicators of health inequalities of socio-economic position (SEP) and mortality have been identified globally. Despite these inequalities, SEP, as a modifiable risk factor, and mechanisms that lie on the causal path between SEP and mortality are not readily targeted for interventions. Dietary habits are one of the mechanisms by which SEP has been linked to chronic disease outcomes and mortality. In the present study, we investigate the relationship between indicators of SEP as potentially having a direct effect on all-cause mortality and an indirect effect via diet and other mediators such as BMI in LIFEPATH, a pan European project comprised of multiple cohorts. Methods To determine factors that may lie on the causal path between SEP exposure and mortality we use both structural equation models (SEM) and counterfactual models. Unique to this work are the detailed exposure data, where the primary exposure is comprised of multiple indicators of SEP, including occupation, income, and education and the main mediator of diet is constructed as dietary patterns via factor analysis. SEM is used to determine important mediators of SEP and mortality and counterfactual mediation methods is used to determine the influence of intervening on dietary patterns to reduce the rate of early mortality. In addition, we compare the two approaches of mediation to infer causality. We compare these results in both a pooled analysis of the seven cohorts nested in LIFEPATH and in the individual cohorts. Results Interestingly, there are two major dietary patterns in the cohorts, western and prudent. We find that there is a direct effect of SEP on all-cause mortality, and that a higher BMI and adherence to a western dietary pattern leads to an increase in the rate of mortality across several populations. For example, in EPIC-Italy the rate of mortality of those who were of lower SEP and obese is 1.4 (95% CI of 1.1, 1.8) compared to those who were higher SEP and non-obese. Additionally, when considering the interaction of BMI and an adherence to a western diet, the rate is 2.2 (95% CI of 1.03, 4.5) in comparison to those with a higher SEP, lower BMI, and non-adherence to a western dietary pattern. Conclusions We conclude that the potential to intervene on SEP and/or mediating factors such as dietary patterns can reduce the rates of premature death. Additionally, methods of structural equation modelling and counterfactual modelling can be used simultaneously to improve our inferences of causality.