Left ventricular hypertrophy leads to heart failure, a serious medical condition associated with high rates of hospitalization and mortality. Limited success with the existing pharmacological treatments necessitates the development of mechanisms-based new therapies to better control the progression from left ventricular hypertrophy to heart failure. The current work investigated the pharmacological potentials and mechanisms of naturally occurring cinnamic acid in the treatment of left ventricular hypertrophy and heart failure. The in vitro findings reveal that cinnamic acid attenuates the hypertrophic responses and mitochondrial dysfunction in the phenylephrine (PE)-stimulated cardiomyocytes. Furthermore, cinnamic acid offsets PE-induced increases in N ⁶ -methyladenosine (m ⁶ A) RNA modification and reductions in the expression of the key m ⁶ A demethylase FTO in cardiomyocytes. Most importantly, FTO knockdown abrogates anti-hypertrophic and mitochondrial protective effects of cinnamic acid in the PE-stimulated cardiomyocytes. The in vivo results further demonstrate that cinnamic acid mitigates left ventricular hypertrophy, left ventricular systolic dysfunction and ultrastructural impairment of cardiomyocyte mitochondria and myofibrils in the mice subjected to transverse aortic constriction (TAC)-induced pressure overload. Moreover, FTO knockdown abolishes these beneficial effects of cinnamic acid in the TAC mice. In conclusion, the work here demonstrates for the first time that cinnamic acid is effective at mitigating pressure overload-induced left ventricular hypertrophy and heart failure in part by modulating the expression of FTO and the level of FTO-dependent m ⁶ A RNA modification in cardiomyocytes. These novel findings warrant further evaluation of cinnamic acid as a pharmacological agent/component to complement the existing treatment of pressure overload-mediated left ventricular hypertrophy and heart failure.