Serotonin (5-HT) participates in the development of cardiac hypertrophy through 5-HT(2A) serotonin receptors. The hypertrophic growth of cardiomyoblasts induced by 5-HT(2A) receptors involves the activation of the Ca(2+) responsive calcineurin/NFAT pathway. However, the mechanism whereby NFAT is activated by 5-HT(2A) receptors remains indeterminate. In this study, we examined whether transient receptor potential canonical (TRPC) channels participate in NFAT activation and hypertrophic response triggered by 5-HT. We demonstrate that TRPC1 expression is upregulated in 5-HT-treated rat cardiomyoblasts whereas TRPC6 is induced in a mouse model of heart hypertrophy. Moreover, TRPC1 knockdown by small interfering RNA inhibits NFAT activation and hypertrophic response mediated by 5-HT(2A) receptors. These findings provide new insights about a mechanistic basis for the activation of the calcineurin/NFAT pathway by 5-HT(2A) receptors and highlight the critical role of TRPC1 in the development of cardiac hypertrophy.