Sexual minority (SM) individuals live in a heterosexist society that denigrates their sexual orientation identity. The stigma and prejudice they regularly encounter is hypothesized to lead to their significantly increased risk for developing mental health disorders. Because of these factors, therapists should be diligent to create an affirming and supportive therapeutic environment but this is often not the case. SM clients frequently report experiencing sexual orientation microaggressions in therapy, such as heteronormative statements, a disregard for their sexual orientation identity, and an assumption that their presenting issues are rooted in their sexual orientation identity. These microaggressions should be viewed as bias manifested as clinical errors because of how they weaken therapeutic alliance, decrease the effectiveness of treatment, decrease utilization intent, and cultivate feelings of shame, anger, and misunderstanding. This article provides empirically supported findings regarding common SM clinical errors and microaggressions, a clinical example of such biases with corrective examples along with the author’s personal reactions, and more general strategies for avoiding microaggressive errors with SM clients. Implications for practice, training, and research are discussed.