This study explored the relationship between therapist personality, self-reported lesbian and gay (LG) affirmative therapy competency, and demonstrated LG affirmative therapy competency utilizing an analogue methodology with 212 therapists-in-training. Participants were randomly assigned to review one of four vignettes that varied the sexual orientation and presenting concern of the characters depicted. The experimental design was a 3 (Openness to Experience: Very High/High/Average) x 2 (Gay/Lesbian Vignette) x 2 (Relationship/Adjustment Vignette) factorial with three dependent variables (i.e., case conceptualization ability, LGB affirmative therapy competency, LGB affirmative therapy self-efficacy), and three covariates (i.e., participant sexual orientation, relationships with LGBT individuals, and number of LGBT clients seen). The relationship between self-reported competency (i.e., self-report measures of competency scores) and demonstrated competency (i.e., case conceptualizations of LG vignettes scores) was also analyzed. Individuals with higher levels of openness to experience exhibited stronger case conceptualization ability; however, contrary to the hypotheses, the four analogue groups did not differ significantly. Case conceptualization ability correlated with self-reported LG knowledge competency. Implications for research, practice, and training are presented. (Contains 6 tables.)