This prospective study examined (a) the mediating roles of Carl Rogers' facilitative interpersonal conditions (i.e., genuineness, empathic understanding, and unconditional positive regard) and (b) the moderating roles of femininity ideology in the association between dispositional authenticity and dyadic relationship functioning using a dyadic approach. Participants, 239 opposite‐gender couples, completed the Authenticity Scale, Barrett‐Lennard Relationship Inventory:mini, Femininity Ideology Scale, and Dyadic Adjustment Scale in two separate phases. Longitudinal data were analyzed using the actor‐partner interdependence (mediation/moderation) model within a structural equation modelling framework. Perceived facilitativeness served as a mediator, channelling the positive associations from dispositional authenticity to dyadic relationship functioning, at both interpersonal and intrapersonal levels. Additionally, femininity ideology emerged as a moderator, influencing the relationships between dispositional authenticity and dyadic relationship functioning in both contexts. These findings underscore the significance of embracing authenticity and transcending traditional femininity ideologies for opposite‐gender partners to thrive cohesively as a dyad. The implications of these findings and avenues for future research are further discussed.