Four types of sibling conflict were identified in actual adolescent sibling discussions: equality and fairness, invasion of the personal domain, intrinsic harm, and relationships. Older [M = 14.97, standard deviation (SD) = 1.69 years] and younger siblings (M = 12.20, SD = 1.90 years) from 144 dyads discussed conflicts during a semi‐structured conflict task. Trained observers coded the topics discussed, and separate observers rated their conflict styles, whereas siblings rated their relationship quality. The proportion of conflicts of each domain differed by dyadic gender composition. Equality and fairness conflicts (and invasion of the personal domain conflicts for sister–sister pairs) were discussed the most frequently whereas intrinsic harm conflicts were associated with destructive conflict styles. Siblings' discussions of conflicts involving intrinsic harm were associated with older siblings' reports of negative relationship quality. The associations between these conflict topics and negative relationship quality were mediated by the siblings discussing the conflicts in destructive ways.