In this letter, a wideband circularly polarized (CP) dielectric resonator antenna (DRA) with flat gain is proposed. The antenna consists of two layers of DRs (the lower part DR1, the upper part DR2), conformal microstrip on DR, and a dielectric substrate. Partitioning the DR into upper and lower sections with different dielectric constants is to equalize the gain within passband. Moreover, the conformal microstrips on both sides of the DR serve as feeders to excite the fundamental TEy111 and TEx111 modes, and high-order TEy113 and TEx113 modes of the DR. In addition, the 90° phase difference between the two resonant modes of each orthogonal pair is achieved by varying the corresponding conformal microstrip heights to improve circular polarization performance. For demonstration, a wideband CP DRA prototype was manufactured and measured. The measurements illustrate that the antenna achieves a wide impedance bandwidth of 38.5 % (3.48–5.14 GHz), an axial ratio (AR) bandwidth of 26.7 % (3.38–4.42 GHz) for left-hand circular polarization (LHCP), and a flat gain reaching 7.2 dBi in the passband.