The diffraction of a dielectric microline pair is optimized by numerical simulations to generate an efficient focusing pattern with a micron-scale footprint. Microlines separated by 1.12 μm are fabricated by two-photon polymerization on a glass substrate, and their diffraction pattern is characterized by three-dimensional wide-field transmission microscopy. A line pair, having a width W=0.40 μm and a height H=0.80 μm, leads to diffraction-limited focusing in the visible spectrum. Depending on wavelength, its focal length, lateral resolution, and depth of focus are in the ranges of 0.8–1.3 μm, 0.22–0.44 μm, and 1.7–2.13 μm, respectively. Such a microlens based on the diffraction of only two subwavelength scatterers could be used for the design of miniature optical sensors with micron and sub-micron pixels.