Prior studies report that couples with higher relationship quality show higher oxytocin (OT) levels, yet other studies report those with higher distress have increased OT. This study investigated these competing predictions in the context of a support enhancement intervention among 34 young married couples (N = 68). Preintervention marital quality (Dyadic Adjustment Scale) was examined for associations with plasma and salivary OT levels 4 weeks apart and for changes between these time points within the intervention group. High relationship quality, not distress, was associated with higher OT in both saliva and plasma at both time points. No significant interaction was found between marital quality and intervention condition; relationship quality and support intervention were both independently associated with higher postintervention OT levels.