Herein, Ni-Co-Mo hybrid oxide/phosphide (NiCoMoO-P) composite self-supported nanoarrays on nickel foam is synthesized through hydrothermal method and in-situ phosphorization process, which are used as a bi-functional nanomaterial for supercapacitors and oxygen evolution reaction (OER) of electrochemical water splitting. The micromorphology and components are optimized, which made the NiCoMoO-P electrode material have fast reaction kinetics, more reactive sites and then positive synergistic effect on the components. As electrode material of supercapacitors, the specific capacity is as high as 1439.3C g−1 at 1 A g−1. The hybrid supercapacitor (NiCoMoO-P//N-rGO) device has a high specific energy of 45.3 Wh kg−1. As electrode materials of OER, NiCoMoO-P shows a low overpotential of 284 mV and a small Tafel slope of 92.5 mV dec–1 at a current density of 100 mA cm−2, showing better OER activity. The results of electrochemical test indicate that the NiCoMoO-P composite self-supported nanoarrays have great potential for the fields of supercapacitors and electrochemical water splitting.