A novel technique to enhance the nucleation of low-pressure diamond on silicon (100) was discussed in this study. It was found that coating the silicon with ballpoint pen ink can greatly increase the diamond nucleation density when the coating was followed by heat treatment at 100 °C–400 °C. Moreover, the optimum enhancement effect was reached when the ink coating was pre-heat-treated at 300 °C × 30 min. Further SEM observation showed that heat treatment at 200 °C-400 °C produced many tiny carbonaceous particles on ballpoint pen ink-coated silicon. Particularly, the nucleation density of diamond on differently treated silicon, such as ink-coated, diamond paste scratched and polished silicon wafers, was compared using the SEM technique. The diamond structure was also characterized by Raman spectroscopy.