Parents-in-law tend to form an important part of individuals’ social capital and thus can be expected to have influence on occupational mobility. With Finnish Census Panel data of almost 100,000 individuals born between 1970 and 1979, followed from the age of 18 to their late thirties, we study whether the resources of the parents-in-law are associated with status attainment. We find that an increase in the resources of parents-in-law is positively associated with a change in one’s own status even after the resources of own parents and those of the partner have been taken into account. Moreover, high parent-in-law resources are more beneficial for individuals from higher social origins than lower origins. Being married and having children is associated with a stronger positive influence of parents-in-law. These findings indicate that parents-in-law can improve socioeconomic success but the effect tends to vary by socioeconomic factors and family structure.