AbstractImmobilization of the reactive metal sites over high surface area porous nanomaterial is a very demanding route in designing novel nanocatalysts for the synthesis of valuable fine chemicals. Here we report an efficient, eco‐friendly and sustainable route for the synthesis of aminophenoxazinone derivatives via oxidative coupling of o‐aminophenols catalysed by a novel mesoporous highly ordered Ni(II)‐complex functionalized mesoporous heterogeneous organosilica catalyst. A novel structurally characterized Ni(II)‐complex derived from 2‐(I‐(2‐(piperizin‐1‐yl) ethylimino) methyl)‐5‐methylphenol ligand has been immobilised over a 2D‐hexagonally ordered functionalized mesoporous SBA‐15 synthesized via surface functionalization of SBA‐15 material with 3‐aminopropyltriethoxysilane (APTES) to obtain the Ni(II)‐nanocatalyst SANI. Its catalytic activity has been explored for three different substrates like o‐aminophenol (OAP), 3‐amino‐4‐hydroxybenzoic acid (CAP) and 2‐amino‐4‐methylphenol (MAP) that produces corresponding phenoxazinone derivatives having the yields of 92, 81 and 85 %, respectively. suggesting wide scope of this supported mesoporous nanocatalyst.