We investigated how learning outcomes of students majoring in interdisciplinary fields differ from those of students in discipline-based majors. We found that students in interdisciplinary majors report less change in Critical Thinking and Need For Cognition than their peers in disciplinary majors, but no difference in change in Positive Attitude Toward Literacy. Students' gains in Critical Thinking and Need For Cognition do not vary by the characteristics of the interdisciplinary major, but some program characteristics influence modest changes in Positive Attitudes Toward Literacy. Future research should address selection effects, develop measures of interdisciplinary learning, and further explore curricular and instructional patterns in interdisciplinary programs.