General personality was assessed of 104 graduate students in school counseling, mental health counseling, and school psychology programs in the United States using the Big Five model of personality domains. The students in three programs reported similarities and differences in their preference and performance in domain knowledge, with more counselor education students preferring counseling courses and more school psychology students preferring quantitative, consultation, and practicum courses. The three groups demonstrated group differences on Extraversion and Openness to Experience domains. The correlational findings confirmed the importance of general personality traits in relation to the academic performance of graduate students. A number of the Big Five NEO Personality Inventory-Revised general personality domains, including Openness to Experience, Neuroticism, and Conscientiousness, were significant predictors of either GRE performance or undergraduate GPA. Theoretical and practical implications of the findings are discussed. The findings suggest that faculty members in counselor education and school psychology programs should consider teaching and mentoring in the ways that they can support their students' nonacademic needs and foster resources and opportunities that would help students to have a more pleasant experience in the programs.