This paper aims to improve understanding of why mixed orientation couples may seek treatment, as well as to support sex and relationship therapists in providing affirmative and respectful services. Mixed orientation relationships, relationships in which partners have different sexual orientation identities, can include a variety of combinations. This paper focuses on mixed orientation ... [Show full abstract] relationships in which one partner identifies as bisexual and the other partner does not. A bisexual identity and a mixed orientation relationship are not inherent problems; however, they can create interpersonal and intrapersonal conflicts that may lead to treatment. Therefore, sex and relationship therapists should be aware of special considerations that could improve treatment with bisexuals in mixed orientation relationships with gay, lesbian, and heterosexual partners. It is important for sex and relationship therapists to take additional care in assessing the meaning of sexual orientation to the bisexual partner, what it means to their non-bisexual partner, and what having a mixed orientation relationship means to the couple seeking treatment. The delicate issue of commitment is respectfully explored, and societal myths related to bisexuality are addressed. Affirmative therapy is proposed as an effective theoretical approach, along with the Ex-PLISSIT Model to guide treatment.