In this study effects of small amount of yttrium addition on grain growth of C.P titanium (single α), Ti-14Mo-3Nb-1.5Zr (single β) and a newly developed Ti-4.5Al-6Nb-2Mo-2Fe (α+β) titanium alloy are investigated. By adding yttrium nano-sized Y2O3 particles are formed in 'in-situ' mode. These particles lead to significant suppression of grain growth in single α and β alloys rather than in the α+β alloy. The results are discussed with regard to conventional grain growth and grain boundary pinning models. It is concluded that yttrium is a potential micro alloying element in titanium alloys and could be used as a grain refining agent.