Nanostructured diamond films are grown on a titanium alloy substrate using a two-step deposition process. The first step is performed at elevated temperature (820 °C) for 30 min using a H 2/CH 4/N 2 gas mixture to grow a thin (approximately 600 nm) nanostructured diamond layer and to improve film adhesion. The remainder of the deposition involves growth at low temperature (< 600 °C) in a H 2/CH 4/O 2 gas mixture. The continuation of the smooth nanostructured diamond film growth during low-temperature deposition is confirmed by in situ laser reflectance interferometry, atomic force microscopy, micro-Raman spectroscopy, and surface profilometry. Similar experiments performed without the initial nanostructured diamond layer resulted in poorly adhered films with a more crystalline appearance and a higher surface roughness. This low-temperature deposition of nanostructured diamond films on metals offers advantages in cases where high residual thermal stress leads to delamination at high temperatures.