This study assessed the co-development of adversity and effortful control based on a sample of Mexican-origin youth (N = 674) and their parents. We used a four-wave longitudinal design and followed target participants from age 10 to 16. At each time point, we measured adversity experienced by the children and their parents and children’s effortful control (self- and parent-reported). We also assessed children’s shift-and-persist coping strategies at ages 14 and 16. Across time, we found slight decreases in child-adversity and slight increases in parent-adversity. Based on bivariate LGC analyses, we found that the strongest effects surfaced for child- (vs. parent-) adversity. Specifically, we found that greater increases in child-adversity were associated with greater decreases in effortful control from ages 10 to 16. Moreover, we found a positive association between initial levels of child-adversity and the slope of effortful control, as well as a cross-sectional negative association between child- and parent-adversity and effortful control (at age 10). We found no evidence of moderation by shift-and-persist coping strategies. In sum, our results suggest that, on average, Mexican-origin youth exposed to more adversity might experience more maladaptive change with respect to effortful control.