Although spirobiacridine (SBA) derivatives show a promising potential not only for thermally activated delayed fluorescent (TADF) emitters but also as host material for blue phosphorescent emitters, only limited research has been reported in the literature. Here, we developed an SBA-based host material, mCN-SBA, which realized a blue phosphorescent OLED with an external quantum efficiency of 19.8%, and Commission Internationale de l'Eclairage (CIEx,y) of (0.16, 0.23).