Tris-(8-hydroxyquinoline)-aluminum (Alq3)–based organic light-emitting diodes with Co electrode are fabricated. The positive magnetic electroluminescence (MEL) and magnetic conductance (MC) are observed in the samples, reaching 4.35% and 1.67% under the field of 42 mT at 50 K, respectively, and the MEL and MC traces can be fitted to non-Lorentzian line shapes. The MEL varies as a function of the Co thickness and reaches the optimal value at 10 nm. The MEL and MC dependence on voltage and temperature is also investigated. The electron-hole pair model and the spin-polarized injection mechanism are used to understand the experimental results.