Titanium alloys are promising candidates for biomedical applications, and alloys based on the Ti-rich side of Ti-Nb-Sn system have presented material properties deserved for orthopedic implant applications. However, to our knowledge, the structural studies related to surface of these alloys are limited. Ti-18Nb-11Sn and Ti-35Nb-4Sn alloys were synthesized, and the influence of thermochemical treatment on the bioactivity was investigated. The alloys were synthesized by arc melting furnace and then were submitted to thermochemical treatment. X-ray diffraction and scanning electron micrograph analysis showed high crystallinity and maintenance of microstructure of the both alloys before and after thermochemical treatment. The results indicated that the Ti-18Nb-11Sn alloy was not demonstrated to be bioactive, while the Ti-35Nb-4Sn alloy slightly presented bioactivity, which increased after the thermochemical treatment. Meanwhile, the Ti-18Nb-11Sn alloy presented a low hardness value, making it not compatible with biomedical applications. However, the Ti-35Nb-4Sn alloy presented an acceptable hardness value for biomedical applications. We believe that the results reported herein suggest that the Ti-35Nb-4Sn alloy may be attractive for designing biomedical devices with improved performances toward the adhesion of apatite.