Objective: To determine the in vivo precision of MRI-based measures of bone and muscle traits at the hip. Methods: Left proximal femoral neck and shaft of 14 participants (5M:9F; age:21-68) were scanned 3 times using a 1.5T MRI. Commercial and custom image processing methods were used to derive bone geometry and strength traits at the proximal femoral neck and shaft along with muscle area of various muscle groups at the shaft site. For precision, root mean square coefficients of variation (CV_rms) and standard deviations (SD_rms) were calculated. Results: At the femoral neck, CV_rms for area-based bone measures ranged between 1.7-5.0%; CV_rms for cortical thickness varied from 4.7 to 5.6%; and CV_rms for bending, torsional and buckling-based strength indices ranged between 4.6-7.1%. At the femoral shaft, CV_rms for bone area ranged between 1.2-3.0%; CV_rms for cortical thickness varied from 1.7 to 2.0%; and CV_rms for bending and buckling-based strength indices ranged between 1.4-3.1%. For muscle area, CV_rms ranged between 1.3-4.5%. Conclusions: MRI-based measures of bone and muscle traits at the proximal femoral neck and shaft demonstrated in vivo precision errors <7.1%. MRI is a promising 3D technique for monitoring changes in bone and muscle at the clinically important hip.