This article examines psychologists’ and social workers’ discourses in relation to international adoptions by single parents in Spain. The analysis suggests that these professionals, who play a key role in moving forward (or not) the adoption process, work with a distinctive notion of “the best interest of the child” in which a heterosexual couple is taken as the normative referent of parental and family relations. The principle of the child's best interest is explicitly defined at the legislative level and is incorporated as part of child protection policies, though in interview discourses it intertwines with many other themes. Our analysis uncovered some diversity in psychologists’ and social workers’ discourses, which seem to be tied to their professional and experiential background, though an argument that portrays single parenthood in negative terms dominates their views. These representations are developed even though the available evidence from post-adoption assessments does not support such bias.