The enrichment behavior of ω clusters in cold-drawn Ti-45Nb (wt.%) filaments is observed and discussed in this paper. The ω phase precipitates as the colonies of almost the same orientation variants near the grain boundary with the size of single particle less than 3 nm in diameter. The enrichment of ω clusters leads to the formation of embrittlement regions in micron dimension along the grain boundary. After polishing and etching, the embrittlement regions transform into macroscopic necklace-like structure along the grain boundary. Furthermore, the volume fraction and mean width of embrittlement regions are measured accurately as a function of diameters. After recrystallization annealing, the enrichment regions disappear and ω particles equally distribute in the matrix.