During Manuel Prado Ugarteche's first government, he was appointed Minister of Public Works and Development, and was a part of the long-standing cabinet headed by Alfredo Solf y Muro (1939–1944).
Along with his brothers, he inherited the former estate of the Counts of San Isidro, which his great-grandfather, José Gregorio Paz Soldán, acquired in 1853.
He enrolled in the Peruvian Democratic Movement, the same one that launched Manuel Prado's candidacy for the 1956 general elections, called by the Odría dictatorship.
In those elections in which the votes of the APRA militants decided Prado's victory, as he had promised to legalize that party.
Beltrán carried out fiscal and financial policy, putting finances in order and stabilizing the currency.