Sections of the Rangers support have long called on the club to recruit the Premiership’s best talent, and the club appear to be acting on that this summer.
Both Shankland and Devlin were among Hearts’ standout players as they came within minutes of a historic Scottish top-flight triumph.
The Ibrox club have signed both without needing to pay a transfer fee and have also plucked manager McInnes from Tynecastle.
“Cammy is obviously a player I know, and I am well aware of what he will offer to Rangers,” the new Ibrox boss said.
“His levels of consistency for me were superb, and he is the type of player that every manager wants in his team.”
Devlin made the most tackles per 90 minutes in the Premiership last season, and among midfielders he ranked second for interceptions, second for defensive contributions and third for recoveries.
Some Rangers fans have expressed concerns about his work on the ball while playing for a team that will dominate possession in most domestic games.
But there were only four Premiership midfielders who completed more accurate passes per 90 minutes than Devlin last season. One of those was Rangers’ Nicolas Raskin.
“He is someone who knows the Scottish league, and nothing will surprise him with what lies ahead,” manager McInnes added.
“I am looking forward to welcoming Cammy to Rangers and working with him again after he returns from his holiday.”