Zero-dimensional perovskite nanostructures have always been shown outstanding applications in recognizing gases and mol. species.Herein, maltose (Malt) was introduced as an encapsulating agent for the synthesis of MAPbBr3 fluorescent perovskite quantum dots (Malt@MAPbBr3 PQDs), showing strong water resistance and good quantum yield (QY).The as-synthesized Malt@MAPbBr3 PQDs have an average size of 7.25 ± 2.63 nm.The structure and elemental composition of Malt@MAPbBr3 PQDs are confirmed by various anal. techniques.The as-synthesized Malt@MAPbBr3 PQDs display remarkable fluorescence characteristics (λEx/Em = 430/535 nm) with QY of 23.74 %.The selectivity of various biomarkers (epinephrine, normetanephrine, creatinine, dehydroepiandrosterone, uric acid, bilirubin, Me nicotinate, γ-aminobutyric acid (GABA), Se-methylselenocystiene, and cortisone) on the fluorescence quenching of Malt@MAPbBr3 PQDs was studied through fluorescence emission spectroscopy.Interestingly, Malt@MAPbBr3 PQDs exhibit a noticeable fluorescence quenching (>90 %) with the limit of detection (8.37 nM) in the presence of GABA.The developed Malt@MAPbBr3 PQDs-based fluorescent sensor is successfully applied to detect GABA in biofluids.