Despite friction between the two parties early last season amid rival IndyCar driver Colton Herta's Formula 1 testing deal with the organisation, O'Ward would go on to sign a new, three-year contract with McLaren.
The announcement came just days before the Mexican finished a close second in the Indianapolis 500, with two wins during the campaign, at Barber Motorsports Park and Iowa.
He would finish the year seventh in the points, one position but more than a full race's worth of points up on team-mate Felix Rosenqvist.
They are joined at an expanded McLaren line-up this year by 2016 Indy 500 winner Alexander Rossi, who moves into the #7 entry with Rosenqvist shifting to Car #6, but O'Ward stays in Car #5 for what will be his fourth season with the squad.
In May, McLaren will also field Tony Kanaan in the Indianapolis 500.