People with higher social anxiety tend to reveal less information about themselves in interactions with strangers, and this appears to be part of a self-protective strategy adopted in situations in which the risk of negative evaluation is judged to be particularly high. This research examined whether a similar style of communication may be adopted by people with higher social anxiety in their close relationships, and whether it may be associated with decrements in the quality (support, depth, conflict) of these relationships. Over 300 people from the community completed a series of online questionnaires measuring social anxiety and depression, and disclosure in and quality of their close friendships and romantic relationships. After controlling for levels of depression, social anxiety was associated with a paucity of disclosure in both romantic relationships and close friendships in females, but not males. There was an indirect association between higher social anxiety and lower relationship quality (lower support, with a trend towards greater conflict) via lower self-disclosure in women's romantic relationships, but not their close friendships. Addressing disclosure in the context of close relationships may assist socially anxious women to develop more fulfilling and harmonious close relationships.