We present the synthesis and properties of Nickelsensor-1 (NS1), a new water-soluble, turn-on fluorescent sensor that is capable of selectively responding to Ni2+ in aqueous solution and in living cells. NS1 combines a BODIPY chromophore and a mixed N/O/S receptor to provide good selectivity for Ni2+ over a range of biologically abundant metal ions in aqueous solution. In addition to these characteristics, confocal microscopy experiments further show that NS1 can be delivered into living cells and report changes in intracellular Ni2+ levels in a respiratory cell model.