They will link up with boss Gareth Jenkins and attack coach Nigel Davies, who had already been appointed to the tour.
Grand Slam winner McBryde will oversee the forwards and will concentrate on developing the set-piece while world record points scorer Jenkins will focus on improving kicking levels.
Wales boss Jenkins said: "The decision to take Robin and Neil to Argentina fits in perfectly with our philosophies on the roles needed within our coaching structure.
"The set-piece is a huge part of the international game and by taking Robin McBryde within the tour party means we are developing specialist coaching skills in that area.
"Kicking is also key to our attacking strategies. It is one of the big challenges of the international game and to have someone of Neil's expertise on board is superb.
"Both coaches are former Lions and are widely respected within the game and by all the players they work with.
"It is a reflection of the coaching development process in place within the WRU that we have such a high standard of personnel already in the system to draw upon.
"Coming on this tour will be an important part of their coaching development."
Leighton Morgan, the WRU's coach development manager, believes the rapid promotion of Jenkins and Robin McBryde is to the benefit of the national side.
He said: "Neil and Robin have undoubted rugby knowledge and experiences and are quickly and professionally combining those qualities with new-found coaching skills and qualifications.
"Having the ability to utilise these individuals at academy level and with various WRU national squads is proving to be hugely beneficial to our game.
"From a WRU coach development point of view, there should be no short-cutting of a coach's professional development.
"But fast-tracking people with Neil and Robin's rugby background is certainly in our best interest."
Jenkins and McBryde were involved with the Welsh under-21s earlier this season and were also used by Scott Johnson to assist the national coaching team during this year's RBS 6 Nations.