The team managed to return to the Primera División for the 1977–78 season. In October 1978, the Instituto Mexicano del Seguro Social (IMSS) acquired the team in a 100% ownership, promising to make the largest football club in the world with 22 million associates throughout the country. With the financial support of the governmental institution, the team experienced successful campaigns with reinforcements such as the old-time idol Horacio Casarín as head coach and the Mexican football's all-time top goalscorer Cabinho, who would become three-time champion striker with Atlante in 1980, 1981 and 1982. Its productive campaigns led them to the 1981–82 final championship match against Tigres UANL, and after regular and extra time, Atlante became runner-up at penalty kicks. Nevertheless, a year later Atlante won its first continental title with the CONCACAF Champions' Cup against Suriname's Robinhood.
