This research explored associations between personality and sexual orientation. In Study 1, we explored whether the Big Five trait dimensions relate to sexual orientation in a nationally representative sample of Australian adults (n = 13,351). Personality differences were observed between those who identified as heterosexual (straight), bisexual, and homosexual (gay/lesbian) on all five measured traits. In Study 2, we conducted an updated systematic review and meta-analysis of personality and sexual orientation. A total of 21 studies (35 independent samples, 262 effect sizes) comprising 377,951 men and women were identified that satisfied inclusion criteria. Results showed that bisexual individuals reported higher levels of openness than homosexual individuals, who in turn, reported higher levels of openness than heterosexual individuals. Bisexual individuals also report lower levels of conscientiousness than both heterosexual and homosexual individuals. Sex moderation effects showed that homosexual men scored higher than heterosexual men on neuroticism, agreeableness and conscientiousness, whereas homosexual women scored lower than heterosexual women on extraversion, agreeableness, and conscientiousness. There was also evidence that personality differences between sexual orientation categories tend to decline with age. These findings align with the gender-shift hypothesis and should be of interest to theorists working in personality science and sexual identity development.