Background Regulator of G protein signaling 6 ( RGS 6) is an important member of the RGS family and produces pleiotropic regulatory effects on cardiac pathophysiology. However, the role of RGS 6 protein in cardiomyocytes during angiotensin II - and pressure overload-induced cardiac hypertrophy remain unknown. Methods and Results Here, we used a genetic approach to study the regulatory role of RGS 6 in cardiomyocytes during pathological cardiac hypertrophy. RGS 6 expression was significantly increased in failing human hearts and in hypertrophic murine hearts. The extent of aortic banding-induced cardiac hypertrophy, dysfunction, and fibrosis in cardiac-specific RGS 6 knockout mice was alleviated, whereas the hearts of transgenic mice with cardiac-specific RGS 6 overexpression exhibited exacerbated responses to pressure overload. Consistent with these findings, RGS 6 also facilitated an angiotensin II -induced hypertrophic response in isolated cardiomyocytes. According to the mechanistic studies, RGS 6 mediated cardiac hypertrophy by directly interacting with apoptosis signal-regulating kinase 1, which further activates the P38-c- JUN N-terminal kinase 1/2 signaling pathway. Conclusions Based on our findings, RGS 6 aggravates cardiac hypertrophy, and the RGS 6-apoptosis signal-regulating kinase 1 pathway represents a potential therapeutic target to attenuate pressure overload-driven cardiac remodeling.