He was born in Concepción on 19 June 1919, the son of Víctor Manuel Rioseco and Matilde Vásquez. He married Carmen Corina Perry de la Maza, with whom he had seven children.
He completed his primary and secondary studies at the Liceo de Concepción. He later enrolled in the School of Medicine at the University of Chile, where he graduated with highest distinction as a surgeon in 1944.
He joined the Radical Party in 1938. In 1950, he became president of the Radical Assembly of Quilleco, in the Biobío Province.
He also served in various public positions: in 1953 he was a councillor of the Caja de Crédito Hipotecario; between 1954 and 1955 he was part of the Corporación de Inversiones; and in 1955 he was a councillor of the National Health Service.
In 1953 he was elected deputy for the 19th Departmental District ("Laja, Nacimiento and Mulchén"), for the period 1953–1957. He was a member of the Standing Committee on Roads and Public Works, and a substitute member of the Radical Parliamentary Committee (1955–1956).
In 1957 he was re-elected deputy for the 19th Departmental District, period 1957–1961, where he served on the Standing Committee on Agriculture and Colonization.
In 1961 he was re-elected once again, serving on the Standing Committees on Finance, Economy and Trade, and as a substitute deputy in the Standing Committee on Internal Government.
In 1965 he was re-elected for a third consecutive term, for the period 1965–1969, where he served on the Standing Committee on Finance.
Manuel Rioseco died on 27 January 2000. Following his death, he was posthumously honored in the Chamber of Deputies of Chile.[2]