Significance Infection with Leishmania ( Viannia ) parasites can have different manifestations, ranging from localized cutaneous to disseminated and mucocutaneous leishmaniasis, that are prone to relapse after the healing. We previously described the association of the endosymbiont Leishmania RNA virus 1 (LRV1) with increased disease severity. Here, we showed that coinfection with the lymphocytic choriomeningitis virus (LCMV) or Toscana virus exacerbated the outcome of Leishmania guyanensis -induced murine leishmaniasis, favoring parasite persistence and dissemination resulting in metastasis. Both endogenous and exogenous coinfections were dependent upon type I interferon responses. Strikingly, LCMV coinfection after the healing of leishmaniasis induced disease reactivation, overriding the protective adaptive immune response. Thus, viral infections may be a significant risk factor contributing to the pathological spectrum of human leishmaniasis.