Reinforced concrete masonry, as the primary lateral load resisting system, is on the rise in North America due to its effective structural capacity, speed of construction and absence of formwork. Fully grouted reinforced masonry shear walls (FG RMSWs) have proved to satisfy ductility demands and withstand moderate-to-high earthquake loads. In contrast, partially grouted reinforced masonry shear walls (PG RMSWs) provide a more economical option for low-to-moderate seismic zones. However, the collapse probability of the latter has not been assessed as thoroughly as the former. Collapse probability refers to a structure’s likelihood to collapse in relation to a given intensity measure. This study aims to evaluate the collapse probability of rectangular PG RMSWs as compared to that of FG RMSWs in moderate seismic zones. Two masonry shear walls were designed according to the NBCC 2020. These walls are a part of a three-storey archetype residential building in Montreal, Canada. One wall was partially grouted, and the other was fully grouted. However, both walls were designed to withstand the same lateral loads. The numerical models of these two walls were developed using the software, Extreme Loading for Structures (ELS). The modeled walls were subjected to incremental dynamic analysis (IDA) using nonlinear time-history analysis with pre-recorded earthquake ground motions. The collapse probability was computed by cumulative distribution of the IDA curves. The results showed that the collapse probability of the PG RMSW was at most 15% higher than its FG RMSW counterpart. However, the PG RMSW would require 40% less material to construct. Therefore, PG RMSWs may be a viable economic alternative to FG RMSWs, while maintaining adequate seismic performance levels.