Nitrate aerosols play an important role in affecting regional air quality as well as the Earth’s climate. However, it is not well represented or even neglected in many global climate models (GCMs). The size distribution of fine and coarse mode nitrate aerosols in GCMs has large uncertainties and it is not well constrained by observations. We recently implemented the Model for Simulating Aerosol Interactions and Chemistry (MOSAIC) module in the U.S. DOE Energy Exascale Earth System Model version 2 (E3SMv2) and the NCAR Community Earth System Model version 2 (CESM2), which was integrated with gas chemistry and aerosol modules to simulate nitrate and its radiative effects. In this study, we evaluate nitrate aerosol concentrations in different size ranges (e.g., PM₁, PM_2.5, and PM₁₀) simulated in E3SMv2 and CESM2, as well as nine GCMs participating in the Aerosol Comparisons between Observations and Models (AeroCom) phase III, against synergetic measurements from long-term ground-based networks (e.g., IMPROVE, EMEP) and aircraft campaigns (e.g., ATom). We also investigate the impacts of dust and sea salt particles on the distribution of fine and coarse mode nitrate, in terms of aerosol mixing state, dust emission, and aerosol size distribution. We find that most AeroCom models have large biases in simulating the distribution of fine and coarse mode nitrate aerosols, especially over dust-dominated and remote ocean regions, while E3SMv2-MOSAIC has much better agreement with observations than most AeroCom models because of using MOSAIC to calculate dynamical mass transfer in both fine and coarse mode. We also find that simulated nitrate aerosols, especially over the tropical and North Atlantic, are sensitive to the treatment of mixing state between dust and sea salt, dust emission fluxes, and emitted dust size distributions.