Stratospheric sulfate aerosol produced by volcanic eruptions plays important roles in atmospheric chemistry and the global radiative balance of the atmosphere. The simulation of stratospheric sulfate concentrations and optical properties is highly dependent on the chemistry scheme and microphysical treatment. In this work, we implemented a sophisticated gas-phase chemistry scheme (full chemistry, FC) and a 5-mode version of the Modal Aerosol Module (MAM5) for the treatment of stratospheric sulfate aerosol in the Department of Energy’s Energy Exascale Earth System Model version 2 (E3SMv2) model to better simulate the chemistry-aerosol feedback following the Pinatubo eruption, and to compare it against a simulation using simplified chemistry (SC) and the default 4-mode version of the Modal Aerosol Module (MAM4). MAM5 experiments were found to better capture the stratospheric sulfate burden from the eruption of the volcano to the end of 1992 as compared to the High-resolution Infra Red Sounder (HIRS) observations, and the formation of sulfate in MAM5FC was significantly faster than in MAM4FC due to the addition of a OH replenishment reaction. Analyses of microphysical processes indicate that more sulfate aerosol mass was generated in total in FC experiments than in SC experiments. MAM5 performs better than MAM4 in simulation of aerosol optical depth (AOD); AOD anomalies from the MAM5 experiment have better agreement with AVHRR. The simulated largest changes in global mean net radiative flux at the top of the atmosphere following the eruption were about -3 W/m² in MAM5 experiments and roughly -1.5 W/m² in MAM4 experiments.