Glycogen synthase kinase-3β (GSK-3β) is a ubiquitously expressed constitutively active serine/threonine kinase that phosphorylates cellular substrates and thereby regulates a wide variety of cellular functions, including development, metabolism, gene transcription, protein translation, cytoskeletal organization, cell cycle regulation, and apoptosis. The activity of GSK-3β is negatively regulated by protein kinase B/Akt and by the Wnt signaling pathway. Increasing lines of evidence show that GSK-3β is an essential negative regulator of cardiac hypertrophy and that the inhibition of GSK-3β by hypertrophic stimuli is an important mechanism contributing to the development of cardiac hypertrophy. GSK-3β also plays an important role in regulating cardiac development. In this review, the role of GSK-3β in cardiac hypertrophy and development and the potential underlying mechanisms are discussed.