The Bears also named Chris Tabor as special teams coordinator and Charles London as running backs coach.
The trio joins new offensive line coach Harry Hiestand as part of the team's staff under new coach Matt Nagy, who was hired on Monday.
Helfrich served as the offensive coordinator for the Ducks from 2009-12 before being elevated to head coach after Chip Kelly left for the Philadelphia Eagles. Helfrich won 33 games in his first three seasons and went to the first College Football Playoff championship game before being fired after going 4-8 during the 2016 campaign.
The 44-year-old Helfrich worked with Tennessee Titans quarterback and former Heisman Trophy winner Marcus Mariota in college. Now, he is expected to aid in the development of Bears quarterback Mitchell Trubisky.
Helfrich has not worked in the NFL but has spent time as an assistant under Kelly and current Tampa Bay Buccaneers coach Dirk Koetter. He worked under Koetter at Boise State in 1998 and then followed him to Arizona State.
Tabor will be making his second stint with the Bears after initially holding the title of assistant special teams coach from 2008-10. He spent the last seven seasons with the Cleveland Browns as their special teams coordinator.
The Browns ranked sixth in kickoff return average against (21.8), seventh in the NFL in punt return average (9.9), ninth in total kick return yards (8,974) and 10th in total return yards allowed (7,627) since Tabor joined Cleveland in 2011.
London has spent nine seasons in the NFL, the past four as the running backs coach for the Houston Texans. He returns to the Windy City after serving as an offensive assistant with the Bears from 2007-09.
In London's first three years with the team, the Texans ranked third in the AFC and sixth in the NFL in rushing. This past season the Texans, finished seventh in the AFC with 115.1 rushing yards per game.
The Bears are looking to become more offensive-minded under Nagy, who served as the offensive coordinator with the Kansas City Chiefs prior to becoming the Bears' new head coach.
The Bears finished 5-11 in 2017 and have missed the postseason in 10 of the last 11 years. They have resided in last in the NFC North four straight seasons.