The news comes a day after Ervine's former Zimbabwean teammate Andy Blignaut signed with Tasmania.
Ervine moved to Perth last month after retiring from the Zimbabwean team over its controversial selection policy and began talks with the West Australian Cricket Association (WACA) three weeks ago.
The 21-year-old is seeking Australian residency and has admitted he would one day like to play cricket for his adopted country.
But Ervine, who lives with his partner Melissa Marsh, daughter of Zimbabwe coach and former West Australian Test opening batsman Geoff Marsh, is initially just hoping to earn a place in the state team.
"I'm exceptionally thrilled and honoured to be awarded a contract with the Warriors," Ervine said on Friday.
"It's a great way to start my new life here and cricket career, but the challenge now is to keep working and earn my place in the team with some strong performances in club cricket."
Ervine, a lower order batsman and medium-pace bowler, has played five Tests and 42 One-day Internationals for Zimbabwe.