The Argentine midfielder was acquired on a free transfer and will be on a one-year contract with the option of a two-year extension.
Club sporting director Nick De Santis told the media last week that the Impact were looking to add one or two players during the summer transfer window to bolster the squad, though without specifying which position he was looking to strengthen.
De Santis saw Bernardello in action during his trip to Argentina in March and is confident that the Rosario native will bring plenty of added quality to the Impact midfield.
"We are very pleased to have finalized the acquisition of a player who has played at the highest levels," De Santis said in a press release. "He fits in well with the identity of the club and we believe he will play an important role for us moving forward."
He added: "Hernán has consistently played between 25 and 30 games a season over his career. He is a player with great quality in midfield that covers a lot of ground, all while displaying great technical skills and great ability to relaunch attacks,"
Bernardello kicked off his professional career in Argentina with Newell's Old Boys in 2006, where he played over 80 games in the top flight. In 2009, he moved to Spanish outfit Almeria and was a starter for the next four seasons in Spain's first and second divisions.
Bernardello spent the 2012-13 season on loan in Argentina with Club Atlético Colón, scoring one goal in 25 appearances.
De Santis told the media via telephone conference Tuesday that the team would still be keeping an eye out for potential reinforecements in the current transfer window.
The Impact have used up all 11 of their foreign spots, with Maxi Rodriguez on the long-term injury list.
Bernardello will be introduced to the media Wednesday morning. He will wear number 23.
Updated: 5:42 p.m. EDT