In 2017, his 728 yards rushing and 826 yards receiving was the first 700/700 season by a Saint, third by an NFL rookie, and the 11th 700/800 season by any NFL player. His 728 rushing yards finished third among rookies behind rushing leader Kareem Hunt and Leonard Fournette. His 81 receptions on the season were first among all rookies and second in the league among running backs behind Le'Veon Bell, and his 826 receiving yards finished first among running backs. Kamara and Ingram became the first running back duo in NFL history to each have over 1,500 scrimmage yards in the same season. Among non-quarterbacks with 100+ carries, his 6.07 yards per rush was the most ever by an NFL rookie, Paul Lowe (1960) and Buddy Young (1948) also achieved this feat, but not as NFL players. Among non-quarterbacks with 100+ carries, his 6.07 yards per rush was the most ever by an NFL rookie, any Saints player, and the third most by any NFL player, trailing Jamaal Charles (6.38 in 2010) and Barry Sanders (6.13 in 1997), since 1980.
In 2017, the Saints finished with an 11–5 record and won the NFC South. In the Wild Card Round against the Carolina Panthers, Kamara had 23 rushing yards, a rushing touchdown, and one reception for 10 yards in the 31–26 victory. In the Divisional Round against the Minnesota Vikings, he had a 14-yard receiving touchdown from Drew Brees in the fourth quarter to put the Saints up 21–20. However, the Saints would lose to the Vikings by a score of 29–24 on the last play of the game. After a spectacular rookie season, Kamara was named the NFL Offensive Rookie of the Year. He was ranked #20 by his fellow players on the NFL Top 100 Players of 2018.