In 1963 he was elected for DC in the Italian Chamber of Deputies, a position he held until 1979, when he became a Senator. He was confirmed in the Italian Senate also in the 1983 general elections. Bisaglia had government positions for some eight years starting from 1972. He was Minister of Agriculture in Rumor V Cabinet, Minister of State Controlled Agencies in Moro IV, Moro V, Andreotti III, IV and V cabinets, and Minister of Industry in the first and second Cossiga governments, as well as in Forlani government of 1980.
Bisaglia began his national career as a collaborator and assistant of fellow Veneto DC politician Mariano Rumor. The alliance between the two fell in 1975, when Bisaglia, with the help of Flaminio Piccoli (DC leader from Trentino) put Rumor in minority in the Dorotei faction within DC that Rumor had himself founded. In 1980, after revelations from Italian Social Movement senator Pisanò, Bisaglia was involved into a scandal connected to oil affairs, together with Sereno Freato, former secretary of Aldo Moro (DC national leader - as well as main member of the Dorotei – and Italy's prime minister who had been killed in obscure circumstances by the Red Brigades in 1979). During a session of the Italian Parliament, Pisanò read a letter by political gossip journalist Mino Pecorelli, in which he asked money from Bisaglia. Pecorelli had been killed by mafia a few years before, and was also involved in the Moro affair, as well as in numerous other ones connected to other DC leader Giulio Andreotti, the masonic lodge Propaganda 2 and the Italian Secret Services. DC forced Bisaglia to resign from minister in December 1980.
Bisaglia died from unclear reasons in June 1984. According to the official reconstruction, he fell into the sea from his boat off Santa Margherita Ligure. At the time, he was president of DC Senators and the process for the oil scandal was being held. There was no autopsy, since (according to some sources) the body was taken off by order of Francesco Cossiga. Bisaglia's body was diagnosed to have "immediately drowned", although the sea was calm and he was a good swimmer. His brother, a priest, also drowned in 1992 in a lake near Domegge. At the time, he was investigating in the former minister's death and, according to one reconstruction, he had come to Cadore to ask the pope (who was in vacation in the area) dispensation from the confessional seal to reveal what he had discovered. Other people who were sojourning in Cadore when the priest died included Giulio Andreotti, Francesco Cossiga and Propaganda 2 Grand Master, Licio Gelli. Bisaglia former personal secretary, Gino Mazzolaio, died in the same circumstance in the Adige River the following year. Another person connected to Bisaglia who died at the time was Ugo Niutta, whom the minister had chosen as boss of Farmitalia and who shared with him knowledges of several Propaganda Due affiliates: he officially committed suicide in London, a few time after his cognizant Roberto Calvi, a banker whose suicide was simulated in that city by order of Michele Sindona, a criminal associated with Andreotti.