Using data on 11,726 respondents from waves 6 (2006) to 21 (2021) of the Household Income and Labour Dynamics in Australia survey and multi-level group mean-centred logistic regression models, we investigated differences in obesity levels among immigrants from English-speaking and non-English-speaking countries relative to those among non-immigrants in Australia, and how those differences changed with duration of residence and age at arrival.When duration of residence was not included, we found significantly smaller odds of being obese among immigrants from both English-speaking and non-English-speaking countries than among non-immigrants. When duration of residence was included, immigrants from non-English-speaking countries had an obesity advantage compared to non-immigrants with up to 19 years of residence in Australia. However, they lost their obesity advantage after 20 years of residence. In contrast, we found no significant difference in the level of obesity between immigrants from English-speaking countries and non-immigrants by duration of residence. We did not find a substantial modification in the association between nativity status and obesity by age at arrival for either non-English-speaking or English-speaking immigrants. In summary, longer residence in the host country was associated with unhealthy weight gain, especially among immigrants from non-English-speaking countries. As the proportion of immigrants from these countries increases in Australia, our findings highlight the need for tailored health and healthcare utilisation services that consider the varying obesity risk profiles of different immigrant groups over time.