This study provides experimental evidence for automatic, relationship-specific social information processing in 13-year-old adolescents. Photographs of participants’ liked, disliked, and unknown peers were used as primes in an affective priming task with happy and angry facial expression probes and in a hypothetical vignette task. For the affective priming, reaction times were faster for congruent than for incongruent prime–probe pairs when the prime visibility was high and the prime–probe stimulus onset asynchrony was long. In the vignette task, participants attributed more hostility toward the protagonist, experienced more anger, and were more likely to retaliate when the disliked peer served as a prime. It is concluded that peer-relational schemas and related affect are activated automatically upon perception of a peer.