Family migration is a common integration process for rural migrants in contemporary China. However, discussions on intra-household decision making in dual-earner migrant families are limited. This study aims to address this gap. The data set from the Rural Urban Migration in China (RUMiC2008–2010) is employed to explore the determinants of household decision making. In addition, logit regression is performed to estimate the probability of wives acting as head of the household under different specifications, and the Blinder–Oaxaca–Fairlie decomposition is utilized to discuss gender differentials in decision-making responsibilities. Income and migration duration differentials between a wife and husband have important influences on the probability of being responsible for household decision making. The squared terms of wives’ and husbands’ income have inverted effects. The gender gap between household decision makers can be largely attributed to structural factors rather than observable characteristics, though bargaining power acts as the main contributor in explained parts. Bargaining theory can account for the probability of wives becoming the household decision maker, and the claim of the specialization approach is also confirmed. Gender inequality among household decision makers is largely attributed to structural factors, such as cultural/social norms, obstacles, or gender discrimination. The establishment of long-term effective mechanisms to improve employment quality for female migrants, the supply of basic public services, and protection of women’s legal rights in the household should be strengthened in the future to elevate the status of female migrants.