Kevin Magnussen, left, and Romain Grosjean have combined to score 76 points so far this season. File photo: Albert Gea / Reuters Kevin Magnussen, left, and Romain Grosjean have combined to score 76 points so far this season. File photo: Albert Gea / Reuters
Haas team principal Guenther Steiner said: "From the very beginning, we needed experienced drivers to hasten the development of our car and our team, and we have two very good and experienced drivers in Romain Grosjean and Kevin Magnussen. We've improved drastically from last year to this year, so retaining both drivers was a pretty easy decision."
The pair have combined to score 76 points this season with Grosjean's fourth place in Austria the team's highest individual finish. Grosjean's future had looked uncertain, however, after he started the year with a run of eight races without a point. Since Austria, which ended that dismal run of form, he has featured more strongly with a sixth place in Germany and seventh in Belgium.
He has also been involved in more than his share of incidents, most recently in Singapore, where he was handed two penalty points for ignoring blue warning flags as Mercedes' race leader Lewis Hamilton tried to lap him. The hold-up threatened to cost Hamilton the lead, with Red Bull's Max Verstappen closing in.
Grosjean now has nine points on his licence, with 12 triggering a mandatory one-race ban, going into Sunday's Russian Grand Prix.
"He should be very careful but I think he knows that," Steiner said on Thursday. "We are on very thin ice at the moment with that."
Magnussen, a former McLaren reject who jumped from Renault at the end of 2016, has grown in stature at Haas and feels fully at home there.
"Both drivers push each other to be better, and their collective feedback allows us to be better," said Steiner. "It's not a coincidence that in their second year as team-mates, Haas F1 Team is having its best year. By keeping Romain and Kevin together, we aim to do even better next year."
Friday's announcement leaves potential vacancies remaining at Red Bull-owned Toro Rosso and Williams, whose Canadian Lance Stroll looks set to switch to Force India.