Tissue engineering technology provides a mean to create fully functional biological tissue equivalents that can grow, repair and remodel in vivo. Our laboratory approach to tissue engineering arterial graft and heart valve equivalents utilizes cell-seeded fibrin gels. However, even after several weeks of static incubation, the mechanical properties of these grafts are much weaker compared to natural tissue. Previous studies in our laboratory and by several others have shown a significant role of mechanical conditioning, particularly cyclic strain on tissue development and enhanced mechanical properties. However, to date no studies have been published with long term cyclic straining of fibrin based tissue constructs. In our current study, we have cyclically strained cylindrical fibrin constructs up to 5 weeks in our custom designed bioreactor system. The studies were conducted at 5% and 10% cyclic strain on porcine aortic valve cells (PAVC) seeded fibrin gel. The samples were harvested at 3 week and 5 week time point. After 3 week of cyclic straining, fibrin constructs had better mechanical properties compared to statically incubated samples at both 5% and 10% strain conditions. The mechanical properties further improved with conditioning up to 5 weeks. Biochemistry analysis showed 33% increase in collagen content after 3 weeks and 100% increase after 5 weeks of cyclic straining. Histological sections also showed increased collagen density in cyclically strained fibrin grafts. This study shows that cyclic strain can be applied to improve mechanical properties of fibrin based tissue constructs with potential to be utilized in both vascular and valvular tissue engineered grafts.