Because the deal was finalized so late, Rossi missed the majority of preseason testing, only getting to complete one session at Sebring International Raceway. Rossi made his IndyCar debut at the season-opening Grand Prix of St. Petersburg, qualifying in the rear of the field in 19th and finishing as the highest-placed rookie in 12th. Rossi then made his oval debut at the next race in Phoenix, running as high as seventh before brushing the wall in the final laps of the race. The highlight of Rossi's first season with the team was winning the Indianapolis 500 after starting from the 11th position on the grid. Rossi was the top rookie in qualifying for the race and led the final few laps as the cars ahead of him on track ran low on fuel and pitted. Rossi managed his fuel over the final stint to win, then ran dry after the finish and had to be towed to victory lane. Rossi would later earn a second top-five finish at the season finale at Sonoma Raceway. Rossi was named the series' 2016 Rookie of the Year on September 19.