Triggerfishes and filefishes in the superfamily Balistoidea rely on coordination of positionally and morphologically asymmetrical dorsal and anal fins to power steady balistiform swimming. The biomechanics of this asymmetrical paired-propulsor systems remain poorly understood, largely due to the difficulty of filming dorsal and anal fins simultaneously. In this study, we used a three-camera high-speed video system to analyze 3D dorsal and anal fin ray swimming kinematics of gilded triggerfish, Xanthichthys auromarginatus. We hypothesized that the morphological asymmetries observed between X. auromarginatus dorsal and anal fins would result in biomechanical asymmetries between these fins during steady swimming. Results revealed that dorsal and anal fin rays exhibit coordinated, yet significantly different kinematic properties both along and between the median fins, with leading edge fin rays providing nearly half of the total propulsive effort. All dorsal and anal fin rays oscillate from left to right with the same frequency, but nearly all other studied kinematic traits differ between rays. The larger dorsal fins exhibit higher amplitude fin ray undulations, lower wave speeds, lower wave lengths, and provide an overall greater percentage of total propulsive effort than the anal fins. Given that X. auromarginatus possess fairly morphologically symmetrical median fins among balistoid fishes, the biomechanical fin asymmetries observed in this study likely occur across a wide range of balistoid species, challenging the long-standing assumption of symmetrical median fin biomechanics in balistoid fishes. Funded by NSF GRFP 1144082 and 1746045, IOS 1425049 and DEB 1541547.