The 50-times capped full back arrived in Wales at the end of October, but has had to wait until this week to get a chance to play because of the November international matches and the Heineken Cup.
He celebrated his 50th and last Test cap in November 2001 against Italy, and has scored 261 Test points. Only four men have played more times for South Africa and only one - Naas Botha - has scored more Test points.
Montgomery made his Super 12 debut in 1996 and made more than 50 appearances in the competition for the Stormers. He also played more than 50 Currie Cup games.
He was originally selected to face Swansea in a Welsh Premiership match at St Helen's on 2 November, but that game was called off because of poor weather. He did play for 40 minutes in a Newport United fixture against Swansea Athletic, but will get his first chance to shine when Newport attempt to build on their opening success in the Premiership when they scored five tries in beating Caerphilly 36-10 on 29 October.
Montgomery takes over the full back role from Shane Howarth, who moves to outside half in place of Jason Strange. The only other change in the back line from the side beaten at London Irish on Sunday is at scrum half, where Ofisa Tonu'u failed a fitness test and is replaced by Dale Burn.
Up front, it is all change in the front row with Rod Snow, James Richards and Adrian Garvey returning to the starting line up and Ian Gough replaces Mike Voyle in the second row. Jason Forster is fit to resume in the back row in place of Joe Powell.
"Last Sunday was a real shock to the system. The week after we showed so much strength, character and resilience to beat London Irish, we simply folded in the face of a pumped up performance from them," said Newport coach Leigh Jones.
"We were a bit complacent after our victory over them the previous weekend. They were wounded animals from the loss at Rodney Parade and the result was a combination of us being poor and them being very good. On the day we were well beaten.
"Our progress up to last Sunday had been steady. I just hope that defeat hasn't set us back."
Newport United's game against Bath United on Monday night was cancelled because Bath couldn't raise a team, but Newport Saracens stepped in at the last minute to fill the gap and give a young Newport side a useful night's work. Wales Under 21 cap Nathan Brew scored three tries on the wing in his first game since October and Wales A caps Jon Pritchard and Andy Powell proved their fitness to take up places among the replacements on Friday night.
NEWPORT RUGBY: Percy Montgomery; Matt Mostyn, Jason Jones-Hughes, Andy Marinos, Hal Luscombe; Shane Howarth, Dale Burn; Rod Snow, James Richards, Adrian Garvey, Simon Raiwalui (captain), Ian Gough, Gareth Gravell, Jason Forster, Steve Ojomoh.
Replacements: Chris Anthony. Paul Young, Mike Voyle, Andy Powell, Llyr Lane, Jon Pritchard, Jason Strange.