Let
$({\mathcal{X}},d,\unicode[STIX]{x1D707})$
be a metric measure space satisfying the geometrically doubling condition and the upper doubling condition. In this paper, the authors establish the John-Nirenberg inequality for the regularized BLO space
$\widetilde{\operatorname{RBLO}}(\unicode[STIX]{x1D707})$
.