A variety of binary Ru-Co mixed oxide nanotubes (RuxCo1-xOy with x = 0.19, 0.33, 0.47, 0.64 and 0.77) were readily synthesized via electrospinning and subsequent calcination. RuxCo1-xOy nanotubes (0 < x < 0.77) were composed of both rutile (Ru in RuO2 is replaced with Co) and spinel (Co in Co3O4 is replaced with Ru) structures. This elemental substitution created oxygen vacancies in the rutile structure and also resulted in the incorporation of Ru3+ in the octahedral sites of the spinel structure. The as-prepared RuxCo1-xOy nanotubes were investigated for oxygen evolution reaction (OER) electrocatalytic activity in 1.0 M HClO4 aqueous solution. RuxCo1-xOy nanotubes with x ≥ 0.47 presented an excellent OER activity comparable to pure RuO2, known to be the best OER catalyst. Even after more than half of the noble/active Ru content was replaced with cheap/less-active Co, Ru0.47Co0.53Oy showed a good OER activity and a greatly improved stability compared to RuO2 under the continuous OER. These attractive catalytic properties of RuxCo1-xOy can be attributed to the relatively large surface area of the tubular morphology and the substituted structures, presenting feasibility as a practical and economical OER catalyst.