Previous research suggests one in five United States (U.S.) adults will engage in
consensual nonmonogamy (CNM) in their lifetime (Haupert et al., 2017). Despite a significant
number of adults engaging in CNM relationships, there is considerable stigma regarding CNM
status. Clients that identify as CNM are marginalized in the process of psychotherapy (Henrich
& Trawinski, 2016; Kisler & Lock, 2019; Schechinger et al., 2018). One previous study found
that one-third of clients who identify as consensually nonmonogamous reported experiencing
inappropriate therapy practices (Schechinger et al., 2018). Inappropriate therapy practices
included their therapist pathologizing their relationship structure or expressing judgmental
attitudes around their CNM relationship. Clients who experienced inappropriate practices were
significantly more likely to terminate therapy prematurely. The present study measures relational
therapists’ (n = 775) attitudes, monogamism sensitivity, and knowledge regarding consensual
nonmonogamy. Treatment practices when working with clients who identify as CNM were also explored through open-ended questions. A simple linear regression revealed that knowledge
of CNM predicted favorable attitudes toward CNM. Furthermore, monogamism sensitivity
strengthened the relationship between knowledge and attitudes. Specialized training was not
significant in predicting knowledge of CNM or attitudes toward CNM. Thematic analysis
revealed four categories related to working with CNM clients in therapy. These categories were
general treatment, helpful practices, unhelpful practices, and perpetuating stigma. Results of both
the qualitative and quantitative data analyses suggest relational therapy training programs should better
prepare clinicians in working with clients who identify as consensually nonmonogamous.
Specifically, in addressing how monogamism influences therapists ’clinical judgement.