Oil sands development in the Athabasca and Cold Lake oil sands regions of Alberta has raised concerns about potential impacts to groundwater and groundwater dependent ecosystems. This review summarizes the current state of understanding as to how oil sands mining and in situ activities can affect groundwater systems using a stressor-mechanism-response framework. Specific oil sands activities and practices are reviewed, and where possible, described in terms of how they can impact hydraulic head, the hydraulic properties of aquifers, recharge and transport of constituents of concern and linked to observed or potential impacts to groundwater quantity and quality. Groundwater is an important component of the water balance in boreal ecosystems, and specific vulnerabilities related to development are reviewed, including water use, landscape disturbance, groundwater withdrawals, tailings pond seepage, deep well disposal and thermal impacts. Knowledge gaps include lack of baseline data and monitoring of the quantity and quality of groundwater discharge to rivers, lakes and wetlands. One key monitoring challenge is attribution of hydrogeologic responses to specific oil sands stressors given the range of other natural and anthropogenic factors contributing to their variability. Quantitative groundwater exchange mapping, regional-scale isotope mass balance assessment, and broader incorporation of isotopic and geochemical tracers for fingerprinting water sources and incorporation of Indigenous Knowledge appear promising for improved effectiveness of monitoring.