Using Kegan's constructive-developmental theory, this study explores to what extent epistemological development is a factor in critical thinking performance and learning in reading and writing among a diverse group of six adult learners. Analysis of a developmental interview, a summative assessment and participant surveys indicated that learners constructing meaning from earlier developmental perspectives demonstrated lower critical thinking in reading and writing, and expressed successes and challenges in accordance with their developmental perspectives. Implications are discussed for supporting critical thinking growth for developmentally diverse adult learners.