The 30-year-old left arm spinner has joined the Black Caps in the UAE as cover for Todd Astle, who has an irritated right knee.
Astle remains a 50-50 chance to play in tonight's first ODI against Pakistan in Abu Dhabi, but was more likely to be available later in the series.
''Todd's made good progress over the past couple of days and with his involvement in both the ODI and test squads, we're keen to give him every chance to be right,'' coach Gary Stead said.
''It does present another opportunity for Ajaz.
''He's impressed us during the UAE tour so far and we have full confidence he can do a job for this team in the 50-over format.''
Also joining the squad are Lockie Ferguson and George Worker, who comes in for the injured Martin Guptill.
''Lockie possesses raw pace and offers something different to the other three quicks in the squad who are predominantly new ball bowlers,'' Stead said.
''He's performed well over the past 12 months and we're hoping he can bring some real aggression to those middle overs in the innings.
''George has been knocking on the door for a while and has hardly put a foot wrong in the chances he has had with the Black Caps.
''We know he's a quality player and this series will be a good test of where he is at.''
Meanwhile all-rounder Corey Anderson was not considered for selection, after missing the final twenty20 with an injured heel.
He will return home for further assessment.
