Vertebrate bone is a conservative tissue, and compressive and tensile strength have been found to be generally similar across tetrapod taxa despite marked variation in limb posture and locomotor patterns. However, the material properties of limb bones from arboreal taxa have not been widely evaluated. Sloths are nearly obligatory in their use of below-branch suspensory locomotion and posture, which places their limb bones under routine tensile loading. It is possible that sloth limb bones have been modified for enhanced tensile strength while compromising some amount of compressive strength, a condition dissimilar to what is typical for upright (or crouched) terrestrial taxa. Long bones from the fore- and hindlimbs of two-toed ( C. hoffmanni) and three-toed (B. variegatus) sloths were loaded in both axial compression and 3-point bending to test this hypothesis. Overall, compared to previously tested taxa, bone strength (60–120 MPa) and elasticity (1–9 GPa) were low under each loading regime with bone loading behavior displaying toughness over stiffness. A clear relationship could not be discerned between the elastic (Young’s) modulus in bending versus compression, whereas both the humerus and femur from sloths showed a correlation between bending and compressive strength. These findings provide support for the hypothesis and infer some degree of elevated tensile strength that would match well with the predicted function of bone in a tensile limb system. Future studies aim to directly load bones in axial tension and observe the microstructure/material composition of sloth bones to verify potential modifications related to increases in tensile strength for suspensory habits.