•Synthesis and characterization of complex Cu-tpmen.•Redox properties of complex Cu-tpmen.•Electrocatalytic oxygen reduction by complex Cu-tpmen.•Electrocatalytic water oxidation by complex Cu-tpmen. The development of catalysts for oxygen reduction reaction (ORR) and water oxidation reaction (WOR) is important for promoting the utilization of renewable energy sources. Catalysts based on Earth-abundant metals are low-cost and benefit the widespread use. Herein a mononuclear copper complex Cu(tpmen)(ClO4)2 (Cu-tpmen) of the pentadentate pyridylalkylamine ligand N,N,N’-tris(2-pyridylmethyl)-N’-methylethylenediamine (tpmen) was synthesized and characterized. The electrochemical properties and the catalysis for the ORR and the WOR by Cu-tpmen in aqueous solutions were studied. Cu-tpmen in pH 7.0 0.1 M phosphate buffer solution (PBS) can boost the ORR with an onset potential at 0.47 V versus the reversible hydrogen electrode (RHE), generating mainly H2O2. The foot-of-the-wave analysis showed that turnover frequency (TOF) of the reduction of O2 to H2O2 mediated by Cu-tpmen was 6.5 × 104 s−1. Meanwhile, Cu-tpmen exhibited catalytic activities for the WOR with the TOF values of 50.9 s−1 (at pH 7.0) and 8.4 s−1 (at pH 10.5). Cu-tpmen was thus a homogeneous bidirectional ORR/WOR catalyst and the reaction mechanisms were proposed. The synergic effect of the flexibility and the electron-donating ability of tpmen benefited the bidirectional catalytic properties of Cu-tpmen. The bidirectional catalytic properties of a copper(II) complex benefited from the synergic effect of the flexibility and the electron-donating ability of the polypyridine ligand. Display omitted