Giardia duodenalis is a protozoan parasite responsible for gastroenteritis in vertebrates, including humans. The prevalence of G. duodenalis is partly owed to its direct and simple life cycle, as well as the formation of the environmentally resistant and infective cysts. Several proteomic and transcriptomic studies have previously analysed global changes during the encystation process using the well-characterised laboratory isolate and genome strain, WBC6. To expand current comparative analyses, this study presents the first quantitative global study of encystation using pathogenically relevant and alternative assemblage A strains: the human-derived BRIS/82/HEPU/106 and avian-derived BRIS/95/HEPU/2041. We have utilised tandem MS/MS with a label-free quantitative approach to compare cysts and trophozoite life stages between strains for variation, as well as confirm universal encystation markers of Assemblage A.