Maharaj has taken 26 wickets in seven Test matches, including two five-wicket hauls.
The 27 year-old also took five for 40 in his final outing of the One Day Cup for the Dolphins before joining the Test squad in New Zealand.
"It has been a really special last six months for me after getting my call-up to the national Test squad in November," Maharaj mentioned.
"My selection for the Champions Trophy came as a bit of a shock, but I'm very grateful for the opportunity.
"I always knew that I wanted to play all three formats of the game for South Africa, but didn't think that I would have played Test cricket and be in the national ODI squad this quickly. I am really looking forward to the challenge."
Maharaj's impressive statistics caught the eye of Proteas convener of selectors Linda Zondi, who also mentioned his batting as another of his assets.
The clean-hitting lower-order batsman has two first class hundreds to his name.
"I played a few seasons of club cricket in the UK and I really enjoy the conditions - except for the cold!" said Maharaj.
"Being selected to make my debut in a competition like the Champions Trophy makes it a little more special I think and we would really like to win it because it has been so long!"
Phehlukwayo, 21, has already represented the Proteas in 14 ODIs and will also be taking part in his first tournament for the national team.
The all-rounder was a member of the famous SA U19 squad that won the World Cup in 2014.
They are joined by Dolphins' evergreen Imran Tahir, who sits atop the limited overs bowling rankings in both T20I and ODI cricket.
Tahir has been a vital cog in the Proteas limited overs set-up for a number of seasons and with 74 ODIs to his name and 127 wickets - it is clear how important he is to the Proteas' white ball efforts.
Following an impressive season with the bat and at the helm of the Dolphins after Morne van Wyk stood down as captain, Khaya Zondo will be in action for the South Africa 'A' side during their tour of the United Kingdom.
Zondo was prolific with the bat in both the four-day and limited overs competitions during the 2016/17 season and another opportunity has come for the calm right-hander to stake a claim for higher national honours.
The 27 year-old has been included in both the four-day and the limited overs squads and will lead the SA 'A' side in their 50-over series against the England Lions.
Proteas ODI squad for three-match ODI series against England and ICC Champions Trophy:
Hashim Amla (Cape Cobras), Quinton de Kock - wicketkeeper (Titans), Faf du Plessis (Titans), AB de Villiers - captain (Titans), JP Duminy (Cape Cobras), David Miller (Knights), Chris Morris (Titans), Wayne Parnell (Cape Cobras), Andile Phehlukwayo (Dolphins), Kagiso Rabada (Highveld Lions), Imran Tahir (Dolphins), Dwaine Pretorius (Highveld Lions), Keshav Maharaj (Dolphins), Farhaan Behardien (Titans), Morne Morkel (Titans)
South Africa 'A' squad for four-day series against England Lions:
Heino Kuhn (Titans), Aiden Markram - captain (Titans), Theunis de Bruyn (Knights), Temba Bavuma (Highveld Lions), Khaya Zondo (Dolphins), Jason Smith (Cape Cobras), Heinrich Klaasen - wk (Titans), Dwaine Pretorius (Highveld Lions), Rudi Second (Knights), Dane Piedt (Cape Cobras), Lungisani Ngidi (Titans), Dane Paterson (Cape Cobras), Duanne Olivier (Knights), Junior Dala (Titans), Beuran Hendricks (Cape Cobras), Dale Steyn (Cape Cobras)