Best practice in early childhood assessment supports a comprehensive multi-method, multi-source measurement approach, with tools validated for use with culturally, linguistically, and economically diverse populations (National Research Council, 2008). This study employed this approach to assess peer social competence in relation to gains in academic readiness for 527 preschool children. Canonical correlations revealed concordance between measures of teacher-reported and observed peer social competence. Path models suggested that these measures were uniquely and differentially associated with gains in direct assessments of academic readiness; with teacher-reported interactive peer play associated with greater gains in vocabulary and observed communication with peers associated with greater gains in listening comprehension. Additionally, observed conflict with peers was associated with significantly fewer gains in alphabet knowledge and mathematics. Findings support the need for a comprehensive measurement approach that includes multiple perspectives and methods for examining peer social competence with culturally and linguistically diverse preschool children from low-income backgrounds. (author abstract)