Advanced to the FedExCup Playoffs and TOUR Championship for the second consecutive season, finishing No. 23 in the FedExCup. Victory at the CareerBuilder Challenge marked his second career PGA TOUR title and one of five top-10s in a season where he made 16 cuts in 20 starts. Also won on the European TOUR. Reached as high as No. 2 in the Official World Golf Ranking. Earned a spot on the Ryder Cup European team for the first time.

Zurich Classic of New Orleans: Teamed with Ryan Palmer to claim his third TOUR victory at the Zurich Classic on New Orleans. At 26-under 262, posted a three-stroke win over Sergio Garcia/Tommy Fleetwood. Team sat T17 after first-round 64 in Four-ball format but captured solo lead through 36 holes at 15-under following a 7-under 65 in Foursomes, the first score of 65 or lower at the event in that format. Went on to share the 54-hole lead with Scott Stallings/Trey Mullinax. Only previous appearance at the event before victory was a missed cut with Wesley Bryan in 2018. 

Mutuactivos Open de Espana: Successfully defended his title at the Mutuactivos Open de Espana, becoming the first player to win in back-to-back years since Max Faulkner in 1953. In his home country of Spain, became the first Spaniard to achieve five European Tour victories in 39 starts or fewer, with Seve Ballesteros’ achieving the feat in 49 starts. Moved to the top of the Race to Dubai Rankings with the victory.
Nationwide Children's Hospital Championship: After finishes of second, third, T4, T5 (twice) and T6, finally broke through with a win at the Nationwide Children's Hospital Championship on the Tour's toughest course of the year. His winning score was 6-under 278, with the field's average score 1.59-over par. Trailed South Africa's Richard Sterne by three shots with four holes to play only to find himself in a playoff after Sterne bogeyed Nos. 15, 16 and 17. A wedge from 75 yards to three feet on the 18th hole at Ohio State University GC's Scarlet Course sealed the victory with both his parents and grandparents in his Sunday gallery. Became the fourth-youngest winner in Tour history, trailing only Jason Day, Patrick Cantlay and Danny Lee.
THE NORTHERN TRUST: Entering the final round with a one-shot lead over Abraham Ancer, carded a 2-under 69 to edge Ancer by one stroke and win THE NORTHERN TRUST for the second time in his career. The win, his seventh on the PGA TOUR, moved him to No. 2 in the FedExCup standings and guaranteed him a spot in the season-ending TOUR Championship. Converted the 54-hole lead/co-lead into a win for the fifth time in seven attempts on TOUR. Became the seventh player to win multiple titles at the event and second to do so in the FedExCup era, joining Dustin Johnson.

On 7 July 2019, Rahm won the Dubai Duty Free Irish Open at Lahinch Golf Club. Rahm trailed 54-hole leader Robert Rock by five shots heading into the final 18 holes of the tournament. Beginning the round at eight-under overall, Rahm registered four birdies on the front nine to make the turn at 11-under overall and three-under 31 for the day. The 2017 Irish Open champion then shot five-under 31 on the back nine, including four birdies and an eagle, to close out the two-stroke victory.[35]