A millimeter‐wave (MMW) dual‐band dual‐sense (DBDS) circular polarization (CP) antenna based on a chiral structure is presented. An arc parasitic patch is loaded around a circular patch to have chiral characteristics. This structure exhibits bi‐isotropy to the electromagnetic wave. The linear polarization (LP) wave passes through the chiral structure and excites the orthogonal left‐handed (LH) and right‐handed (RH) CP waves. The antenna is fabricated and measured. The LHCP radiation is achieved in the range between 23.75 and 24.25 GHz, and the RHCP radiation is between 27.75 and 28.25 GHz. The realized gains reach 6.9 dBic at 24 GHz and reach 7.1 dBic at 28 GHz. The proposed antenna has a profile of 1.044 mm (0.08 λ) and occupies an area of 0.54 λ × 0.54 λ, λ is the free‐space wavelength at the lower frequency and is convenient for array design.