Akodon spegazzinii is found in northwestern Argentina, in the provinces of Salta, Catamarca, Tucumán, La Rioja, and Mendoza, at altitudes of . Although its main distribution is in the northern provinces of Salta, Tucumán, and Catamarca, there are also scattered records from the more southern provinces of La Rioja and Mendoza, where it is likely restricted to patches of wet habitat. "Akodon alterus" has been reported from Jujuy, but this record was likely based on misidentified specimens of "A. boliviensis", and records of "Akodon spegazzinii" from Jujuy were based on misidentified "A. sylvanus". "Akodon spegazzinii" is known from a paleontological site in
Formosa Province up to 45 °C The tropical weather is characterized with uniform annual rains in the east (1000 mm annual), while in the rest of the country winter is a drier season (80 mm). The humidity variation results in the jungle vegetation on one side, and the Chaqueño forest in the other. The limit with the Salta Province is known as the "Impenetrable" ("Impenetrable"). Formosa's protected areas are the Río Pilcomayo National Park and the Formosa National Reserve. Coincidentally, part of the province is the antipode to northern Taiwan, which was also known as "Formosa". (Taiwan was named "Formosa" by European