The selective signaling of hypochlorous acid by dithiane-protected [corrected] pyrene-aldehyde was investigated. Dithiolane derivative of pyrene-aldehyde was efficiently deprotected by hypochlorous acid to its corresponding aldehyde, which resulted in a prominent UV-vis and turn-on type fluorescence signaling. The signaling was not affected by the presence of other common alkali, alkaline earth metal ions, and anions. Interference from Hg(2+) ions could be successfully circumvented by using Chelex-100 resin. Dithiane [corrected] also provided selectivity toward hypochlorous acid over other commonly used oxidant of hydrogen peroxide.