Abstract: The structural, electronic and magnetic properties of Co₁₀ nanowire encapsulated inside (12,0) boron nitride nanotube (BNNT) were investigated by the first-principles calculations. A approximate regular triangle cross section shape is formed for outer (12,0) BNNT in the relaxed geometry structure of Co₁₀/BNNT(12,0) system. Binding energy analysis shows that the combining processes of Co₁₀/BNNT(12,0) system is exothermic, and therefore the Co₁₀ nanowire can be encapsulated into semiconducting (12,0) BNNT and form a stable hybrid structure. The charges are transferred from Co₁₀ nanowire to more electronegative BNNT, and the formed Co-N bonds have polar covalent bond characteristics. The magnetic moment of Co₁₀/BNNT(12,0) system is smaller than that of the freestanding Co₁₀ nanowire. The stable Co₁₀/BNNT(12,0) system exhibit higher magnetic moment and half-metal character implying which can be useful for a wide variety of next-generation magnetic data storage and spintronics devices.