This study explored the association between cumulative ecological risk and academic achievement among adolescents from economically disadvantaged families and the mediating role of coping style and moderating effect of grit on this relationship. We recruited a sample of 509 students from economically disadvantaged families (classified as below the local income threshold) from Hunan Province, China. We conducted three surveys over two years (October 2018-October 2020). The results revealed that (1) cumulative ecological risk has a negative impact on the academic achievement of adolescents from families; (2) coping styles mediate the association between cumulative ecological risk and academic performance; and (3) grit can buffer the impact of cumulative ecological risk on one's way of coping, but the buffering effect of grit diminishes as the level of cumulative ecological risk increases.