The deposition of a well adherent diamond film on titanium and its alloys is always complicated due to the different thermal expansion coefficients of the two materials, the complex nature of the interlayer formed during diamond deposition, and the difficulty in achieving very high nucleation density. In this work well-adherent and smooth nano-crystalline diamond film was successfully deposited on pure titanium substrate by microwave plasma assisted chemical vapor deposition (MWPCVD) method in CH4/H2 environment. It is found that the average grain size was less than 20 nm with a surface roughness value as low as 28nm. Of particular interest in this study was the exceptional adhesion of approximately 2μm-thick diamond film to the metal substrate as observed by indentation testing up to 150 kg load. Experimental results on growth mechanism and obtaining good adhesion are discussed.