Cardiogenic shock frequently leads to death even with intensive treatment. Although the leading cause of cardiogenic shock is acute coronary syndrome (ACS), the clinical characteristics and the prognosis of ACS with cardiogenic shock in the present era still remain to be elucidated. We analyzed clinical characteristics and predictors of 30-day mortality in ACS with cardiogenic shock in Japan. The Japanese Circulation Society Cardiovascular Shock registry was a prospective, observational, multicenter, cohort study. Between May 2012 and June 2014, 495 ACS patients with cardiogenic shock were analyzed. The primary endpoint was 30-day all-cause mortality. The median [interquartile range; IQR] age was 71.0 [63.0, 80.0] years. The median [IQR] value of systolic blood pressure (SBP) and heart rate were 75.0 [50.0, 86.5] mm Hg and 65.0 [38.0, 98.0] bpm, respectively. Multivariable analysis showed an odds ratio (OR) of 4.76 (confidence intervals; CI 1.97–11.5, p < 0.001) in the lowest SBP category (< 50 mm Hg) for SBP ≥ 90 mm Hg. Moreover, age per 10 years increase (OR 1.38, CI 1.18–1.61, p = 0.002), deep coma (OR 3.49, CI 1.94–6.34, p < 0.001), congestive heart failure (OR 3.81, CI 2.04–7.59, p < 0.001) and left main trunk disease (LMTD) (OR 2.81, CI 1.55–5.10, p < 0.001) were independent predictors. Severe hypotension, older age, deep coma, congestive heart failure, and LMTD were independent unfavorable factors in ACS complicated by cardiogenic shock in Japan. A prompt assessment of high-risk patients referring to those predictors in emergency room could lead to appropriate treatment without delay.