Importance: Cardiogenic shock after acute myocardial infarction (AMI) is associated with high mortality, particularly among patients with multivessel coronary artery disease. Recent evidence suggests that use of multivessel percutaneous coronary intervention (PCI) may be associated with harm. However, little is known about recent patterns of care and outcomes for this patient population. Objective: To evaluate patterns in the use of multivessel PCI vs culprit-vessel PCI in AMI and cardiogenic shock and outcomes in the US from 2009 to 2018. Design, Setting, and Participants: This cohort study identified all patients in the CathPCI Registry) with AMI and cardiogenic shock who had multivessel coronary artery disease and underwent PCI between July 1, 2009, and March 31, 2018. Exposures: Multivessel or culprit-vessel PCI for AMI and shock. Primary Outcomes and Measures: The primary outcome was in-hospital mortality. Temporal trends and hospital variation in PCI strategies were evaluated, while accounting for differences in case mix using hierarchical models. As a secondary outcome, the association of PCI strategy with postdischarge outcomes was evaluated in the subset of patients who were Medicare beneficiaries. Results: Of 64301 patients (mean [SD] age, 66.4 [12.5] years; 20366 [31.7%] female; 54538 [84.8%] White) with AMI and shock at 1649 US hospitals, 34.9% had primary multivessel PCI. In the subgroup of 48943 patients with ST-segment elevation myocardial infarction (STEMI), 31.5% underwent multivessel PCI. Between 2009 and 2018, this percentage increased by 6.7% per year for AMI and 5.8% for STEMI. Overall, multivessel PCI was associated with a greater adjusted risk of in-hospital complications (odds ratio [OR], 1.18; 95% CI, 1.14-1.23) and with greater in-hospital mortality in patients with STEMI (OR, 1.11; 95% CI, 1.06-1.16). Among Medicare beneficiaries, multivessel PCI use was not associated with postdischarge 1-year mortality (51.5% vs 49.8%; risk-adjusted OR, 0.97; 95% CI, 0.90-1.04; P =.37). Significant hospital variation was found in the use of multivessel PCI, with a higher multivessel PCI rate for similar patients across hospitals (median OR, 1.37; 95% CI, 1.33-1.41). Patients at hospitals with high rates of PCI in STEMI use had higher risk-adjusted in-hospital mortality (highest vs lowest hospital multivessel PCI quartile: OR, 1.10; 95% CI, 1.02-1.19). Conclusions and Relevance: This cohort study found that multivessel PCI was increasingly used as the revascularization strategy in AMI and shock and that hospitals that used multivessel PCI more, especially among patients with STEMI, had worse outcomes. With recent evidence suggesting harm with this strategy, there appears to be an urgent need to change practice and improve outcomes in this high-risk population.