Ramirez, 42, will continue to work with the club's major and minor league hitters on the fundamental and mental aspects of hitting, according to a team release.
Last season, Ramirez joined Triple-A Iowa as a player/coach and received positive reviews in his role. He played 19 seasons in the majors, batting .312 with a .411 on-base percentage and a .585 slugging percentage, but was suspended for performance-enhancing drug use in 2009.
"Manny got rave reviews from everyone he worked with," Cubs president of baseball operations Theo Epstein said Tuesday. "... He did a great job of fitting in, sharing his wisdom and experience and being a good influence.
"He was very open and honest with guys on what not to do from his past and lessons that he learned along the way."
Epstein said that Ramirez would be in uniform with the Cubs at Wrigley Field for about one homestand every month.
"He is really smart," new Cubs manager Joe Maddon said. "We had great conversations about hitting. I thought we developed a good relationship. He knows how to get a point across. It's another resource to draw upon. He's a lot of fun to be around."
Ramirez played for Maddon with the Tampa Bay Rays in 2011 until he was suspended in early April.
Youkilis, 35, will serve as the Cubs' scouting and player development consultant. He retired in 2013 after an 11-year major league career.
Youkilis will assist the front office by scouting amateur and professional hitters in Northern California and will work with hitters in the minor league system under the direction of the hitting coordinator.