ABSTRACT: The influence of weight on in-hospital events of acute myocardial infarction complicated with cardiac arrest (AMI-CA) is understudied. To address this, we utilized the National Inpatient Sample database (2008-2017) to identify adult AMI-CA admissions and categorized them by BMI into underweight, normal weight, and overweight/obese groups. The outcomes of interest included differences in in-hospital mortality, use of invasive therapies, hospitalization costs, and hospital length of stay across the three weight categories. Of the 314,609 AMI-CA admissions during the study period, 268,764 (85.4%) were normal weight, 1,791 (0.6%) were underweight, and 44,053 (14.0%) were overweight/obese. Compared to 2008, in 2017, adjusted temporal trends revealed significant increase in prevalence of AMI-CA in underweight (adjusted OR {aOR} 3.88 [95% CI 3.04-4.94], P<0.001) category, and overweight/obese AMI-CA admissions (aOR 2.67 [95% CI 2.53-2.81], P<0.001). AMI-CA admissions that were underweight were older, more often female, with greater comorbidity burden, and presented more often with non-ST-segment-elevation AMI, non-shockable rhythm, and in-hospital arrest. Overweight/obesity was associated with higher use of angiography, PCI, and greater need for mechanical circulatory support whereas underweight status had the lowest use of these procedures. Compared to normal weight AMI-CA admissions, underweight admissions had comparable adjusted in-hospital mortality (adjusted OR 0.97 [95% CI 0.87-1.09], P=0.64) whereas overweight/obese admissions had lower in-hospital mortality (adjusted OR 0.92 [95% CI 0.90-0.95], P<0.001). In conclusion, underweight AMI-CA admissions were associated with lower use of cardiac procedures and had in-hospital mortality comparable to normal weight admissions. Overweight/obese status was associated with higher rates of cardiac procedures and lower in-hospital mortality.