This study demonstrates the control of neuronal activity using nitrogen-doped ultrananocrystalline diamond (N-UNCD), a photoelectric material capable of converting light into electric fields. We highlight the role of N-UNCD in regulating neuronal growth via near-infrared illumination, demonstrating the generation of stable photocurrents that enhance neuronal survival and neurite outgrowth, and foster a more active, synchronized neuronal network. Whole transcriptome RNA sequencing reveals that diamond substrates improve cellular/substrate interaction by upregulating extracellular matrix and gap junction-related genes. Our findings underscore the potential of conductive diamond as a robust and biocompatible platform for non-invasive and effective neural tissue engineering.