Partner‐specific perfectionistic concerns (PC) include concern over mistakes, self‐criticism, and socially prescribed perfectionism as it pertains to one's partner. The social disconnection model proposes that PC influences well‐being indirectly through interpersonal problems. Thus, we hypothesized that social negativity (expressed anger, hostility, and rejection) would mediate the relationship between dyadic PC and subjective well‐being. Data from 203 romantic dyads (92.1% heterosexual) were collected using self‐report surveys and a four‐wave, 4‐week longitudinal design. Participants were predominantly female (53.1%), young (M = 22.69 years), and Caucasian (82.3%). Data were analyzed using an actor‐partner interdependence model with multilevel structural equation modeling. There were significant actor effects at the between‐subjects and within‐subjects levels, and significant partner effects for the relationship between PC and social negativity at the within‐subject level. Social negativity mediated the relationships between PC and both negative affect and life satisfaction. However, positive affect was more weakly related to PC and social negativity. The social disconnection model was supported. PC was positively associated with one's own social negativity and evoked hostile behaviors from one's partner. Hostile, rejecting behaviors reduced the well‐being of the actor, but not the partner. Results suggest perfectionism may be best understood within an interpersonal context.