Background: Previous studies have shown reductions in the volume of emergency department visits early in the COVID-19 pandemic, but few have evaluated the pandemic’s impact over time or stratified analyses by reason for visits. We aimed to quantify such changes in British Columbia, Canada, cumulatively and during prominent nadirs, and by reason for visit, age and acuity. Methods: We included data from the National Ambulatory Care Reporting System for 30 emergency departments across BC from January 2016 to December 2022. We fitted generalized additive models, accounting for seasonal and annual trends, to the monthly number of visits to estimate changes throughout the pandemic, compared with the expected number of visits in the absence of the pandemic. We determined absolute and relative differences at various times during the study period, and cumulatively since the start of the pandemic until the overall volume of emergency department visits returned to expected levels. Results: Over the first 16 months of the pandemic, the volume of emergency department visits was reduced by about 322 300 visits, or 15% (95% confidence interval 12%–18%), compared with the expected volume. A sharp drop in pediatric visits accounted for nearly one-third of the reduction. The timing of the return to baseline volume of visits differed by subgroup. The largest and most sustained decreases were in respiratory-related emergency department visits, visits among children, visits among oldest adults and non-urgent visits. Later in the pandemic, we observed increased volumes of highest-urgency visits, visits among children and visits related to ear, nose and throat. Interpretation: We have extended evidence that the impact of the COVID-19 pandemic and associated mitigation strategies on emergency department visits in Canada was substantial. Both our findings and methods are relevant in public health surveillance and capacity planning for emergency departments in pandemic and nonpandemic times. [See related article at www.cmaj.ca/lookup/doi/10.1503/cmaj.231156][1] [1]: /lookup/volpage/195/E1157