<p>Direct laser writing (3D printing) is rapidly emerging as a versatile method for fabricating novel 3D structures that are needed for quantum computing, superconducting devices, selective coatings, and biomedical sensors. Here, we have created 2D patterns with potential for 3D diamond structures by direct laser writing lithography, which are carbonized in an inert Ar atmosphere at 540°C and then used as nucleation sites for diamond growth via hot-filament chemical vapor deposition (HFCVD). An array of 3D structures was fabricated via a two-photon polymerization process using a photo-polymeric resin on Si (100) and sapphire (0001) substrates. These 3D structures carbonized by thermal annealing show approximately 45–55% sp³ content, as confirmed by Raman spectroscopy and x-ray photoelectron spectroscopy (XPS) analytical techniques. As per the end application of the device, the computer-aided design (CAD) of the structure can be modified to innovative shapes that can be carbonized to provide selective nucleation sites for placing diamond crystallites at the desired locations, which is an important component for device fabrication. The diamond crystallites show a distinctive Raman peak upshift in the range of 1333–1335&#xa0;cm⁻¹ with a full width at half maximum of ≤ 5&#xa0;cm⁻¹, indicating some strain across the diamond and Si (100) substrate. A fourfold growth morphology with {111} planes of diamond crystallites is shown by high-resolution scanning electron microscopy (HR-SEM), which correlates with the &lt;100&gt; growth of diamond. Additionally, we show the possibility of creating 3D structures in Q-carbon phase with embedded nanodiamond crystallites via pulsed laser annealing (PLA) of carbonized structures.</p> Graphical Abstract <p></p>