A direct measurement of the photon yield of the 148.9‐keV gamma of123Xe has been made. The value obtained: 48.0±1.0 photons of 148.9‐keV emitted per 100 decays of123Xe. The advantage of the present method is that it is a direct measurement and does not rely upon conversion coefficient measurements in123Xe and the summing of many gamma intensities. The half life of123Xe was measured and found to be 2.23±0.02 h.