The purpose of this study was to evaluate histologically and biomechanically the interface between porous hydroxyapatite ceramics and a tendon grafted into ceramics, and to compare the interface in two ceramics with different porous structures: interconnected porous calcium hydroxyapatite ceramics (IP-CHA) with an effective porosity index (interpore diameter > 20 microm) of 63.6%, and porous calcium hydroxyapatite ceramics with less interconnection (HA-L) with an effective porosity index of 5.5%. The tendon-IP-CHA complex and the tendon-HA-L complex were implanted into the bone defects made in both knees of rabbits. With IP-CHA, abundant fibrous tissue, including vessels and collagen fiber continuity, was observed inside interface-region pores. The amount of osseous tissue in interface-region pores increased over time, and at 24 weeks after operation, the tendon was in direct contact with the osseous tissue in IP-CHA. With HA-L, the amount of fibrous tissue in interface-region pores was low and did not increase. The results of biomechanical analysis revealed that the maximum tendon pull-out load from IP-CHA was significantly higher than that from HA-L. With the porous hydroxyapatite ceramics having highly interconnecting porous structure, a bioactive interface was achieved between ceramics and grafted tendon. On the basis of these results, we conclude that bone defects, including tendon insertion, can be reconstructed using IP-CHA.