Canada's cellulosic ethanol biorefinery concept is supported by federal and provincial government legislative ethanol mandates as well as enabling science and innovation policies for technology development to support the economic and sustainable production of cellulosic ethanol and co-products from Canada's abundant supply of lignocellulosic agricultural and forestry biomass. In particular, the development of pretreatment, hydrolysis, and fermentation technologies is regarded as a critical integrating step for the commercialization of cellulosic ethanol biorefinery business concepts. These critical steps are necessitated by the chemical structure of lignocellulosic biomass comprising carbohydrate polymers and lignin which constrains the ability of enzymes to convert these polymers into fermentable sugars without expensive and highly capital intensive pretreatment processes. This paper reviews science and innovation efforts by Canadian researchers in finding solutions to these constraints, in particular the development of hydrolysis and fermentation technologies. This paper also highlights the role of multi-institutional science and innovation collaborative approaches for advancing Canada's cellulosic ethanol biorefinery concept further downstream. While highlighting Canada's scientific progress, this review also outlines technology commercialization lags between basic research and full scale commercialization of a Canadian cellulosic ethanol biorefinery concept. Although this paper focuses on the near-term goal of cellulosic ethanol production, it nevertheless recognizes that ethanol is only the first step in the longer-term goal aimed at a full integrated bioconversion of lignocellulosic biomass into biofuels and a wide range of value-added biochemicals and biomaterials, consistent with the cellulosic biorefinery concept.