A pyrene-based fluorescent chemosensor APSB [N-(pyrene-1-ylmethylene) anthracen-2-amine] was designed and developed by a simple condensation reaction between pyrene carboxaldehyde and 2-aminoanthracene. The APSB fluorescent sensor selectively binds Fe3+ in the presence of other metal ions. Apart from this, APSB shows high selectivity and sensitivity toward Fe3+ ion detection. The detection limit for APSB was 1.95 nM, and the binding constant (Kb) was obtained as 8.20 × 105 M-1 in DMSO/water (95/5, v/v) medium. The fluorescence quantum yields for APSB and APSB-Fe3+ were calculated as 0.035 and 0.573, respectively. The function of this fluorescent sensor APSB can be explained through the photo-induced electron transfer mechanism which was further proved by density functional theory studies. Finally, a live-cell image study of APSB in HeLa cells was also carried out to investigate the cell permeability of APSB and its efficiency for selective detection of Fe3+ in living cells. © 2022 The Authors. Published by American Chemical Society.