Fearful and self-conscious subtypes of shyness have received little attention in the empirical literature. Study aims included the following: (1) determining whether fearful shyness predicted self-conscious shyness, (2) describing development of self-conscious shyness, and (3) examining genetic and environmental contributions to fearful and self-conscious shyness. Observed self-conscious shyness was examined at 19, 22, 25, and 28 months in same-sex twins (MZ = 102, DZ = 111, missing zygosity = 3 pairs). Self-conscious shyness increased across toddlerhood, but onset was earlier than predicted by theory. Fearful shyness (observed [6 and 12 months] and parents’ reports [12 and 22 months]) was not predictive of self-conscious shyness. Independent genetic factors made strong contributions to parent-reported (but not observed) fearful shyness (additive genetic influence = .69 and .72 at 12 and 22 months, respectively) and self-conscious shyness (additive genetic influence = .90 for the growth model intercept). Results encourage future investigation of patterns of change and inter-relations in shyness subtypes.