This investigation proposes that theory of mind (ToM) may be related more strongly to change in friendships than peer acceptance in late middle childhood through early adolescence, and examines the relation between ToM and anxious solitude. Fourth grade ToM was tested as a predictor of change in reciprocated friendships, peer acceptance, and anxious solitude from 4th to 7th grade, and, conversely, reciprocated friendships, peer acceptance, and anxious solitude in 3 rd grade were tested as predictors of 4th grade ToM. Gender moderation of these relations was evaluated. Participants were 688 American public-school children (51.5% girls), 193 of whom completed a ToM questionnaire in 4th grade. In 3rd-7th grade children and their peers reported reciprocated friendship, and peers reported peer acceptance and anxious solitude annually. A multi-group (gender split) autoregressive cross-lagged panel analysis modeled relations between ToM and reciprocated friendship, peer acceptance, and anxious solitude over time. Consistent with hypotheses, girls' more advanced 4th grade ToM predicted incremental gains in their number of friendships two years later, but not their peer acceptance. In contrast, boys' more advanced 4th grade ToM did not predict change in their number of friendships or peer acceptance over time. Gender differences in the relation between ToM and friendship are discussed in the context of gender-specific peer relations