The variants of primary progressive aphasia (PPA) are predominantly diagnosed on the basis of specific profiles of language impairments. Deficits in other cognitive domains and their evolution over time are less well documented. This study examined the cognitive profiles of the PPA variants over time and determined the contribution of cognition on functional capacity.Longitudinal performance on the Addenbrooke's Cognitive Examination-III (ACE-III) total and cognitive subdomains were investigated in 147 PPA individuals (41 logopenic [lv-PPA], 44 non-fluent [nfv-PPA], and 62 semantic variants [sv-PPA]). The relative contribution of ACE-III subdomain scores to overall functional capacity over time was identified using mixed and hierarchical regression modelling.The annual rate of global ACE-III decline was twice that in lv-PPA than in nfv-PPA and sv-PPA, despite lv-PPA performing intermediate to the other variants at baseline assessment. Notably, attention and visuospatial subdomains declined faster in lv-PPA than in nfv-PPA and sv-PPA; and memory impairment was more severe in lv-PPA than in nfv-PPA at all time points. Functional decline was comparable across PPA variants; however, the contribution of cognition on functional capacity varied across variants and over time.The cognitive profiles of the PPA variants are distinct at baseline and over time. Crucially, cognitive decline in lv-PPA was more widespread and pervasive than in nfv-PPA and sv-PPA. Our findings also demonstrate the complex interplay between cognition and functional capacity. This study underscores the importance of routinely assessing cognition and functional capacity in PPA to improve diagnostic accuracy and provide targeted support services.