Neuropathic pain is a type of chronic pain caused by injury or dysfunction of the nervous system, without effective therapeutic approaches. Mesenchymal stromal cells (MSCs), through their paracrine action, have great potential in the treatment of this syndrome. In the present study, the therapeutic potential of MSC-derived conditioned medium (CM) was investigated in a mouse model of neuropathic pain induced by partial sciatic nerve ligation (PSL). PSL mice were treated by endovenous route with bone marrow-derived MSCs (1 × 106), CM, or vehicle. Gabapentin was the reference drug. Twelve hours after administration, neuropathic mice treated with CM exhibited an antinociceptive effect that was maintained throughout the evaluation period. MSCs also induced nonreversed antinociception, while gabapentin induced short-lasting antinociception. The levels of IL-1β, TNF-α, and IL-6 were reduced, while IL-10 was enhanced on sciatic nerve and spinal cord by treatment with CM and MSCs. Preliminary analysis of the CM secretome revealed the presence of growth factors and cytokines likely involved in the antinociception. In conclusion, the CM, similar to injection of live cells, produces a powerful and long-lasting antinociceptive effect on neuropathic pain, which is related with modulatory properties on peripheral and central levels of cytokines involved with the maintenance of this syndrome.