Masoe replaces injured captain Richie McCaw for the two Tri-Nations tests against the Springboks, with the loose forward mix to be reassessed before tests against Australia next month.
"Chris' experience against South Africa and knowledge of our systems mean he's the right choice," All Blacks coach Graham Henry said today.
"But we may want to take a different approach against Australia.
"We'll look at form and fitness and the team's plan again in a couple of weeks."
Meanwhile, Chiefs lock Kevin O'Neill will also join the squad as cover for Ali Williams, who is recovering from a sprained ankle.
"The medical staff is reasonably positive that Ali will be available this weekend, but it is sensible to have extra cover just in case," Henry said.
Henry also confirmed loose forward Rodney So'oialo as the All Blacks captain in McCaw's absence.
"Rodney leads with actions more than words," Henry said.
"He has the respect of everyone in the team and plenty of experience as captain of the Hurricanes."
McCaw suffered a serious ankle injury during New Zealand's 44-12 win over England in Christchurch on June 21, ruling him out of action for an expected six weeks.
New Zealand's second test against South Africa is in Dunedin on July 12.
