He studied besides discharging his duties at his workplace and he graduated from the Faculty of Economy of the József Nádor University of Technology and Economics in 1946.

Horváth joined the Independent Smallholders, Agrarian Workers and Civic Party (FKGP) in 1942.

He participated the national resistance in 1944 against the Arrow Cross regime as a member of the "Free Life" Students' Movement.

He was appointed leader of the Budapest District XIII branch of the Independent Smallholders' Party in February 1945.

He became a member of the Provisional National Assembly from the FKGP's Greater Budapest Regional List on November 4, 1945.

He was arrested on trumped-up charges relating to the Hungarian Community (Magyar Közösség) case on January 16, 1947 and he was sentenced to four years of forced labour.

[5] Horváth returned to Hungary at the invitation of Viktor Orbán, leader of Fidesz in 1997.

He obtained an honorary doctorate from the University of Economics and Public Administration of Budapest where he lectured as guest professor.

After the death of László Varga in 2003, János Horváth was the oldest sitting Member of Parliament.

In that capacity he opened the inaugural meeting of the National Assembly in 2006 and 2010 as the Father of the House.