The three new players have charted contrasting paths towards their first national contract.
Jamieson burst onto the international stage this home summer with Player of the Match performances in his debut ODI and Test series against India.
Patel possesses a formidable first-class record and has been in the New Zealand Test mix for the past 18 months, featuring most prominently away from home.
Conway, 28, had a phenomenal past two seasons topping the domestic batting charts. He had migrated from South Africa in 2017 and becomes eligible for national selection in August.
"It's really exciting to offer contracts to Kyle, Ajaz and Devon who have all impressed over the past 12 months," New Zealand's selection manager Gavin Larsen said.
"Devon's form with the bat across all three formats these past two seasons made him impossible to ignore and he's going to be a great option to add to the batting mix. We see Ajaz as the incumbent test spinner at present and he'll be looking to stamp his mark on that spot after some strong efforts with the ball in the subcontinent," he added.
Jimmy Neesham, Will Young and Tom Blundell have all retained their contracts after being added to the list last season.
New Zealand contract list for 2020-21:
Tom Blundell, Trent Boult, Devon Conway, Colin de Grandhomme, Lockie Ferguson, Martin Guptill, Matt Henry, Kyle Jamieson, Tom Latham, Henry Nicholls, James Neesham, Ajaz Patel, Mitchell Santner, Ish Sodhi, Tim Southee, Ross Taylor, Neil Wagner, BJ Watling, Kane Williamson, Will Young.