This paper reports an assessment of the performance of calcium sulfoaluminate-based cementitious materials in chloride-rich environments while addressing the importance that insightful mix proportioning can have on chloride ingress performance. Belite-calcium sulfoaluminate pastes and mortars were prepared at 4 different calcium sulfate to ye'elimite ratios (ranging from 0 to 2) and the properties of the matured matrix (i.e. porosity and binding capacity) were assessed. A comparative assessment was made of the effective chloride diffusion coefficient in belite-calcium sulfoaluminate mortars through commonly used migration (NT Build 492) and diffusion (NT Build 443) accelerated testing protocols. The influence of paste porosity was apparent in NT Build 492, where lower performance was noted for the low sulfate mixes. These results were in contrast with NT Build 443 observations and are attributed to the short testing period of the migration method in which the potential binding affinity of the hydrates is restricted.