A low-profile circularly polarised (CP) antenna with wide 3 dB axial ratio beamwidth (ARBW) is proposed in this study. The possibilities of widening the 3 dB ARBW of single diagonal slot-loaded conventional CP antenna have been explored successfully by incorporating a pair of rectangular slots along the diagonal line of a square patch antenna. The design parameters and the symmetrical arrangement of this pair of slots across the centre of the patch are crucial to adjust and achieve the wide 3 dB ARBW with high CP purity. Coupling between the two diagonal slots provides nearly equal Eθ and Eφ radiation patterns over a large angular range, and hence the 3 dB ARBW has been enhanced by 85.71 and 55.4% for φ = 0° and φ = 90° planes, respectively, in comparison to the conventional slot-loaded CP antenna. The minimum 3 dB ARBW of 208° and a maximum of 230° have been achieved across different planes of radiation φ = 0°, 45°, 90°, and 135° with a minimum axial ratio of 0.20 dB only. The absolute planar antenna of size (0.29 × 0.29 × 0.013)λ03, where λ0 is the free-space wavelength corresponding to the CP frequency, has been fabricated and tested. The measured and simulated results show fair consistency to each other. © The Institution of Engineering and Technology 2019.