Abstract Heteroatom doping can drastically alter the electronic characteristics of graphene quantum dots (GQDs), thus resulting in unusual properties and related applications. Herein, we develop a simple and low-cost synthetic strategy to prepare nitrogen-doped GQDs (N-GQDs) through hydrothermal treatment of GQDs with hydrazine. The obtained N-GQDs with oxygen-rich functional groups exhibit a strong blue emission with 23.3% quantum yield (QY). Compared to GQDs, the N-GQDs exhibit enhanced fluorescence with blue-shifted energy. Due to the selective coordination to Fe3+, the N-GQDs can be used as a green and facile sensing platform for label-free sensitive and selective detection of Fe (III) ions in aqueous solution and real water samples. The N-GQDs fluorescence probe shows a sensitive response to Fe3+ in a wide concentration range of 1–1945μM with a detection limit of 90nM (s/N=3). Interestingly, it is also found that both dynamic and static quenching processes occur for the detection of Fe3+ by N-GQDs, while the quenching effect of Fe3+ on the fluorescence of GQDs is achieved by affecting the surface states of GQDs.