The fluoride ion-sensing behavior of a novel and strongly phosphorescent Ir(III) complex bearing boryl groups was investigated. A THF solution of 1,3-dibromobenzene was stirred under an Ar atmosphere and cooled to -78°C. The temperature was raised to room temperature and the reaction mixture was stirred overnight. Concentration and subsequent silica gel column purification gave a white powder in 71% yield. The high steric demand imposed on the dimesitylboryl group enabled size-selective anion-boron binding interactions. It was observed that the complex exhibited both extremely high selectivity toward fluoride ions and high-efficiency two-color phosphorescence behavior at room temperature, enabling calorimetric and ratiometric fluoride ion sensing.