The trio have left the club with immediate effect as Tony Pulis prepares to finalise the appointment of a new backroom staff after succeeding Alan Irvine.
Director of football administration Richard Garlick said: “The club would like to place on record its deep appreciation for the contribution of Keith, Rob and Dean within the coaching structure.
“Keith and Dean have been here a number of years and took over first-team control in a caretaker capacity during a difficult period last season. They played a key role in stabilising the team.
“Rob joined at the start of the season and became a valued member of the coaching set-up.
“Changes in personnel are part of football life and it is obviously sad to say farewell to three popular and respected members of staff.
“We wish to thank them for their efforts and wish them all the very best in their future endeavours.”
Downing became first-team coach under Roy Hodgson in March 2011 before being elevated to assistant head coach in December 2011 following the departure of Michael Appleton to become Portsmouth manager.
Following Steve Clarke’s departure in December 2013, Downing took over at The Hawthorns in a caretaker capacity – his side winning one and drawing three of five Premier League games – before Pepe Mel was installed.
Kiely had been Albion goalkeeper coach since March 2010.
The former Republic of Ireland No 1 initially joined the club as a player in January 2007, helping the Baggies to the Championship play-off final later that year, which ended in defeat to Derby.
He made 88 appearances for Albion as a player before becoming goalkeeper coach under Roberto Di Matteo.
Kelly, meanwhile, joined the club with Irvine as the Scot???s joint-assistant head coach alongside Downing in June.
He took caretaker charge after Irvine’s dismissal, overseeing the 1-1 draw at West Ham before Pulis assumed control on January 1.