This paper analyses the relationship between poverty and union situation of couples in Mexico from 1996 to 2014. Using a logit model, cohabitation is estimated to increase the probability of being poor compared to being married, and based on a logit Oaxaca decomposition a couple who cohabit has on average up to 12 percentage points higher probability of being poor than spouses who are married. When the same analysis is performed to compare divorced men and women, women have a higher marginal probability of being poor. The Oaxaca decomposition shows that this difference is due to the fact being a female, varying from 2.2% to 3%, but the total gap due to the sex differential is 11%. The difference could be explained because the existence of marital regimes where the law establishes that the assets in case of divorce accrue to whoever works and pays for them. Given that women devote more time to unpaid work like household chores, men are the owners of the assets. This fact creates poverty with gender bias in the case of divorce.