Despite being a valuable step in the evaluation of resource potential in prospective unconventional reservoirs, porosity in the mudstone intervals of the Horn River Group of the Central Mackenzie Valley has not yet been studied in detail. This project focuses on the Husky Little Bear N-09 core, located approximately 35 km southwest of Norman Wells, Northwest Territories. Bulk porosity measurements, N2 adsorption experiments, and scanning electron microscope (SEM) imaging are used to assess the pore size distribution and the relative abundance of different pore types. By combining these results with mineralogical data and thermal maturity proxies, we evaluate the most significant controls on porosity in this interval and interpret porosity origins and evolution. Findings from this study are compared to those of other producing North American mudstone reservoirs, with the ultimate aim of contributing to our understanding of hydrocarbon storage and reservoir potential in the Horn River Group of the study area.