Binary offset carrier (BOC) signal tracking is one of the challenging problems in future global navigation satellite systems (GNSS) including Galileo and global positioning system (GPS), because false lock could be generated in the tracking procedure due to multiple side-peaks in BOC autocorrelation. Multipath mitigation is another challenging problem in GNSS systems, because the presence of multi-path signals gives a range error. Recently, a novel tracking scheme for the BOC signal was proposed by Garin [8]. However, it can not completely resolve the ambiguity problem due to the false lock and has not enough multipath mitigation performance. Moreover, Garin?s scheme is applicable to only BOC(n, n). In this paper, we propose a novel unambiguous multipath mitigation scheme. The proposed scheme is applicable to various BOC signals (i.e., BOC(kn, n)) and does not incur false lock point in the tracking procedure. In addition, the proposed scheme has appropriate multipath mitigation performance than traditional and Garin?s schemes.