A method of designing a compact circularly polarized (CP) patch antenna is proposed based on a composite right/left-handed (CRLH) transmission line (TL) unit-cell. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) nicked at antenna floor for realizing inductance in parallel and a gap slotted at the center of a sticked plate for realizeing serial capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the size of the proposed antenna. Simultaneously, the asymmetry of the CSRR brings about a parasitical mode which crosses the +1st-order mode orthogonally by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna form a CP property. The experimental results show that the size of the proposed antenna is 0.389λg×0.389λg, and the impedance bandwidth and the axial ratio bandwidth are of 16.08% and 1.52% respectively. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift and ground via, and is easy to design and process.