Angiotensin (Ang) II participates in the pathogenesis of heart failure through induction of cardiac hypertrophy. Ang II‐induced hypertrophic growth of cardiomyocytes is mediated by nuclear factor of activated T cells (NFAT), a Ca²⁺‐responsive transcriptional factor. It is believed that phospholipase C (PLC)‐mediated production of inositol‐1,4,5‐trisphosphate (IP₃) is responsible for Ca²⁺ increase that is necessary for NFAT activation. However, we demonstrate that PLC‐mediated production of diacylglycerol (DAG) but not IP₃ is essential for Ang II‐induced NFAT activation in rat cardiac myocytes. NFAT activation and hypertrophic responses by Ang II stimulation required the enhanced frequency of Ca²⁺ oscillation triggered by membrane depolarization through activation of DAG‐sensitive TRPC channels, which leads to activation of L‐type Ca²⁺ channel. Patch clamp recordings from single myocytes revealed that Ang II activated DAG‐sensitive TRPC‐like currents. Among DAG‐activating TRPC channels (TRPC3, TRPC6, and TRPC7), the activities of TRPC3 and TRPC6 channels correlated with Ang II‐induced NFAT activation and hypertrophic responses. These data suggest that DAG‐induced Ca²⁺ signaling pathway through TRPC3 and TRPC6 is essential for Ang II‐induced NFAT activation and cardiac hypertrophy.