Bismuth dendrites were electrodeposited onto an activated glassy carbon electrode and the resulting modified electrode was employed in the electrochemical detection of para-nitrophenol, an aromatic aquatic pollutant. The carbon electrode was activated by cycling between − 2.0 and 2.0 V vs. SCE to create active sites that can promote the electron transfer reaction. Bismuth dendrites were subsequently deposited at a potential of − 1.0 V vs. SCE for 400 s. A near 5-fold increase in the peak current associated with the conversion of para-nitrophenol (100 μM) to para-hydroxyaminophenol was obtained on activating the glassy carbon electrode. A more impressive 7-fold increase in the peak current was achieved on decorating the activated glassy carbon with bismuth dendrites. Calibration curves with linear regions from 1.6 to 170 μM and between 0.005 and 1.6 μM para-nitrophenol were obtained to give a LOD value of 0.18 nM and a sensitivity of 29.4 μA μM− 1 cm− 2 for the lower concentration range. Good repeatability, reproducibility and selectivity were achieved, while recovery values between 96.5 and 106.7 % were obtained in water samples. In addition, the bismuth dendrites were easily regenerated through an oxidation step at 0.6 V vs. SCE followed by a 400 s electrodeposition period in 1.0 mM Bi(III).