Until late-2017, the Canadian worked in F1 for Red Bull Racing, most recently as an aerodynamicist.
Before that, however, he had been a race engineer for drivers including Ricciardo and fellow Australian Mark Webber.
McLaren SP has not yet specified what role Ward will take up, having announced his arrival with a brief message on social media.
“Arrow McLaren SP is delighted to welcome Gavin Ward to the team,” read that communication.
“Gavin will play a key role in our long-term ambitions in the NTT IndyCar Series.”
Newgarden finished second in the 2021 IndyCar Series, one position ahead of McLaren SP's Pato O'Ward.