Non-invasively monitoring the mechanical property change of the engineered tissue constructs in vivo may help evaluate and feedback tissue scaffold design. In this paper, ultrasound elasticity imaging (UEI) was applied to detect mechanical property changes of the implanted polyurethane tissue constructs on a rat abdominal defect. Bi-axial mechanical measurements on the excised tissue/scaffold constructs were performed for comparison with the UEI results. An increase in overall stiffness along with tissue ingrowth was observed in 4 and 8weeks using both UEI and direct mechanical testing. While, pure scaffold embedded in 10% gelatin showed decrease in stiffness with degradation. Histopathology confirmed tissue in growth such as collagens.