We introduce a chemical reflow method to fabricate diamond microlenses. First, photoresist pillars developed by photolithography are reflowed in organic solvent vapor atmosphere at 20 °C to form spherical segment patterns on diamond substrate. The effects of chemical solvent type and reflow time on photoresist pattern profiles are investigated. Second, via dry etching, diamond microlenses are fabricated by transferring the spherical segment pattern into substrate. Furthermore, these diamond microlenses demonstrate low numerical aperture, well-controllable curvature, and good imaging performance with projecting experiment.