The electrochemical oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are two critical processes for energy conversion technologies, including water electrolysis, fuel cells, and metal-air batteries. For technological implementation, both reactions require highly active and stable electrocatalysts. Here, we report the simultaneous functionalization of carbon nanotubes with bimetallic manganese-vanadium OER/ORR catalytic sites, and nitrogen/sulfur atoms to increase electrical conductivity. A bottom-up fabrication route using polyoxometalate metal precursors enables facile and scalable deposition of bimetallic catalysts on the carbon nanotubes. Electrocatalytic OER/ORR studies show the high activity and stability of the composite under alkaline aqueous conditions, and comparable performance to commercial PVC (20 wt.%) was observed. Initial mechanistic analyses shed light on the effects of the bimetallic functionalization as well as the N/S-doping of the carbon nanotubes. In future, the use of heterometallic polyoxometalate precursors could allow the variation of metal types and atomic ratios, which could lead to well-defined bimetallic composites for various electrochemical processes.