We examine how the family environment is associated with aspects of the Fragile X syndrome phenotype during childhood, adolescence, and adulthood. Mothers of children (n = 48), adolescents (n = 85), and adults (n = 34) with Fragile X syndrome participated in a multisite study. For children and adults with Fragile X syndrome, the presence of warmth and positivity and the absence of criticism were associated with fewer behavior problems. Although a higher level of criticism was significantly associated with greater behavior problems, there were only trend-level associations between levels of warmth and positivity and behavior problems during the adolescent years. The provision of family psychoeducation programs, which can reduce parental criticism, would likely benefit both the individual with Fragile X syndrome and the family.