The Gravity Recovery and Climate Experiment (GRACE) and its Follow-On mission (GRACE-FO) have a combined 23 years of observations, enabling long-term terrestrial water storage anomaly (TWSA) trend estimation. The heterogeneous hydrological dynamics of Canada, including arid plains, high-mountain glaciers, and the Great Lakes, pose a challenge for characterization of water resources, which is crucial for United Nations Sustainable Development Goal 6, Clean Water and Sanitation, and Goal 15, Life on Land. The purpose of this research is to use a novel data-driven approach to delineate regions of Canada with similar interannual TWSA fluctuations and assess the long-term and interannual TWSA trends in these regions. Variability of linear trend estimation is investigated using three different GRACE/GRACE-FO products, as well as three different models of glacial isostatic adjustment (GIA). The relationships between regional interannual TWSA fluctuations and 17 atmospheric and oceanic indices are evaluated in order to understand potential drivers of TWSA change. A change in linear trend is identified for most of Canada around 2020, indicating an overall drying trend. The Arctic Oscillation, Atlantic Meridional Mode, Pacific Decadal Oscillation, Indian Ocean Dipole, and West Pacific Index are identified as having relatively high correlations with interannual TWSA trends in certain regions of Canada, though the correlations are spatiotemporally heterogeneous. This research highlights the complexity of interpreting long-term TWSA trends in Canada using GRACE/GRACE-FO considering the interactions between climate modes operating at various spatiotemporal scales.