Although perceived ethnic/racial discrimination is well established as a risk factor for depressive symptoms in ethnic minority youth, few studies have examined their longitudinal relationship over time. This study examined whether a negative attributional style, positive ethnic/racial affect, and emotional reactivity moderated the longitudinal relationship of perceived peer or adult discrimination and depressive symptoms in a sample of African American and Latino high school students (n = 155). African American and Latino youth who experienced increases in perceived peer discrimination also reported greater depressive symptoms over time, but positive ethnic/racial affect buffered the longitudinal association. Emotional reactivity also served as a significant moderator but only of the baseline association between perceived peer discrimination and depressive symptoms. Thus, perceived ethnic/racial discrimination appears to play a significant role in the development of depressive symptoms for ethnic minority youth, especially those who start high school with lower levels of positive ethnic/racial affect.