The existence of an “immigrant health paradox” is well established in the UK: although the non-UK born are generally healthier than their UK born counterparts upon arrival, their health declines with increasing time in the receiving country and across generations. Currently two hypotheses explain this trend: negative acculturation, adopting negative health behaviours due to increased time spent with white British, and/or exposure to discrimination, which leads to the adoption of unhealthy behaviours as a coping strategy. Due to a lack of data, both of these hypotheses are usually tested in isolation, using only time since arrival and generational status as proxies for acculturation and exposure to discrimination. Using data from Understanding Society this paper provides a first estimate of the impact of these two causal mechanisms on health behaviours across time and immigrant generations. We model the probability of smoking, binge drinking, walking regularly, and eating fruits and vegetables on a) exposure to white British measured as a function of friendship composition, the ethnic composition of the residence, and social participation; and b) exposure to discrimination as self-reports of harassment in a variety of domains.