Limb bone biomechanics are expected to reflect differences in the habitats and functional tasks that vertebrate species encounter. Measurements of bone strain can test how skeletal loads change among different habitats and behaviors. We evaluated changes in strain magnitudes between level walking and climbing in green iguanas, a lizard that frequently climbs trees. However, changes in loading may also include shifts in the orientation of the neutral axis through limb bone cross-sections, reflecting changes in the direction of bending. We used strain gauges implanted on the humerus and femur to evaluate changes in neutral axis orientation for iguanas between level and inclined (60 deg) surfaces. We predicted that, as the anatomical planes of the limbs reorient relative to gravity when animals climb, neutral axis orientation should rotate by an amount comparable to the incline of the slope. Our results did not bear out this prediction. For the humerus, we found little change in neutral axis orientation during steps in either substrate condition – the axis began the step oriented from anterior to posterior, and reoriented only slightly from anteroventral to posterodorsal. In contrast, femoral neutral axes began steps oriented from anteroventral to posterodorsal, but then shifted parallel to the ventral surface during steps, reflecting medial rotation of the limb. However, these patterns of change for the femur were maintained across different trackway conditions, and were largely similar to patterns observed previously in quadrupedal reptiles using sprawling posture (e.g. Alligator, Tupinambis). Results for both limbs thus suggest that arboreal habitats may not have strong effects on neutral axis orientation and bending direction of limb bones during locomotion.