Introduction: Despite structural distinction between the transverse and oblique heads of the adductor pollicis, in vivo testing continues to consider the adductor pollicis as functionally simplistic. As a muscle's architecture is a strong indicator of function, in this study we aimed to determine whether the physiological cross-sectional areas (PCSAs) of both heads were uniform. Methods: Classical, microdissection, and chemical dissection procedures were conducted on 10 cadaveric left hands to determine structural origin and insertions. Architectural measures of muscle length (Lm), muscle weight (Wm), fascicle length (Lf), sarcomere length (Ls), and pennation angle (θ) were used to calculate PCSA and fascicle length:muscle length ratio (Lf:Lm). Results: The oblique head had greater variation in attachments, significantly greater PCSA (P = 0.008), and smaller Lf:Lm (P = 0.001) than its transverse counterpart. Conclusions: Muscle architecture suggests the oblique head has greater potential for force generation, and the transverse has greater potential for joint excursion.