Co‐seismic ionospheric disturbance (CID) may provide insights on understanding the coupled nature of earthquake–atmosphere geophysical processes. In this study, the CIDs following the Mw 7.7 Jamaica earthquake on January 28, 2020 are detected about 12 min after the main shock by the dual‐frequency Global Positioning System measurements. Significant CIDs at two azimuths are observed from satellite PRN03, 04 and 26 with spreading out at 3.54, 3.51 and 3.48 km/s respectively, which are close to the spreading speeds of Rayleigh waves recorded by the seismographs. The significant CID signals are found in south near‐field area and southwest far‐field area. Furthermore, CID characteristics are analyzed in terms of amplitude, elevation and azimuth angle, waveform, and frequency domain. Results show that CIDs are observed by PRN03, 04 and 26 at low elevation angles (<35°) in infrasonic wave frequency domain and the average negative amplitudes of CIDs observed by PRN26 are larger than −0.08 TECU, while the CID amplitudes observed by PRN03 and PRN04 are about −0.05 and −0.07 TECU, respectively. Moreover, the azimuthal asymmetry of CID amplitude in SW and SE azimuths and different initial polarities in disturbance signals are found and discussed from tectonic and nontectonic factors. The relations among CID, Rayleigh wave and focal mechanism are interpreted. The upward propagating secondary acoustic wave triggered by the seismic Rayleigh wave from earthquake is the main source of CIDs. These results confirm that strike‐slip earthquake can also generate pronounced co‐seismic ionospheric disturbances.

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