In January 2019, Oscar De La Hoya instructed Golden Boy president Eric Gomez to start negotiating a deal for a third fight between Golovkin and Álvarez. Golden Boy had already booked in 4 May, Cinco De Mayo weekend at the T-Mobile Arena. A few days later, Gomez posted on social media, after preliminary talks with Golovkin's team, he felt as though Golovkin did not want a third fight. On 17 January, it was announced that Álvarez would take part in a middleweight unification bout against Daniel Jacobs on May 4, 2019.
On 21 March, Golovkin advised that he wanted to fight the best of the middleweight division, regardless of belts. He wanted to close out the remainder of his career, not chasing titles, but to only fight the best and be the best middleweight. On 16 April, Golovkin announced he would fight 35 year old Canadian boxer Steve Rolls (19-0, 10 KOs) on 8 June 2019, at Madison Square Garden in New York at a catchweight of 164 pounds. Other names in the running to fight Golovkin were Brandon Adams (21-2, 13 KOs), Kamil Szeremeta (19-0, 4 KO) and former world champion Hassan N'Dam. It was then reported that Adams would challenge Jermall Charlo (28-0, 21 KOs) instead. Speaking to Fight Hub TV, Loeffler explained Rolls was chosen as Golovkin's opponent to increase subscriptions in Canada. On 24 April, Golovkin released a statement announcing he had split with longtime trainer Abel Sanchez, after nine long years. Sanchez called Golovkin 'Greedy and ungrateful', also advising ESPN, Golovkin had offered him a pay cut, which he refused. In May, during a press conference, Golovkin revealed Johnathon Banks as his new trainer. Banks was best known for having trained former world heavyweight champion Wladmimir Klitschko. Golovkin weighed 163 pounds, and Rolls came in at 163¾ pounds. Golovkin's official purse was listed as $2 million, however it was reported he would earn closer to $15 million. Rolls was paid $300,000.
On 5 October 2019, Golovkin defeated Ukrainian Sergiy Derevyanchenko by unanimous decision for the vacant IBF and IBO middleweight titles at Madison Square Garden, New York. After a tentative start to the opening round, which saw both fighters sizing each other up with probing jabs, Golovkin fired off a six punch combination ending with a right hook to Derevyanchenko's head, dropping the Ukrainian with 1 minute left in the first round. Derevyanchenko rose to his feet within seconds, showing no signs of being hurt. The knockdown appeared to spur Derevyanchenko into action as he began to answer Golovkin's punches with his own shots for the remainder of the round. In round two, Derevyanchenko began putting three and four punch combinations together behind a single and double jab, while Golovkin stuck to single punches, landing the occasional eye-catching hook. Towards the end of the round, Golovkin opened a cut above Derevyanchenko's right eye. The action replay appeared to show the cut was caused by a left hook, however, the New York State Athletic Commission deemed it to be the result of an accidental clash of heads, meaning if the fight was stopped due to the cut before the fourth round then the fight would be ruled a no contest, after the fourth, the result would be determined by the scorecards with a technical decision rather than a technical knockout win for Golovkin if the cut was deemed to be the result of a punch. After Golovkin started the opening seconds of the third round as the aggressor, Derevyanchenko quickly fired back to the body, appearing to hurt Golovkin as he backed up and kept his elbows tucked in close to his body to protect his mid-section. Derevyanchenko took advantage of Golovkin's defensive posture, landing several clean punches to the former champion's head. Towards the end of the round Golovkin had some success with a couple of sharp hooks to the head and a right uppercut. Golovkin was the aggressor for the majority of the fourth round, having partial success, with Derevyanchenko picking his moments to fire back with two and three punch combinations and continuing to work the body. In the last minute of the round, Derevyanchenko appeared to momentarily trouble Golovkin with a straight-left hand to the body. At the beginning of the fifth round, the ringside doctor gave the cut above Derevyanchenko's right-eye a close examination before the action resumed. Derevyanchenko controlled the pace of the round with a high punch-output, continuing with three and four punch combinations with lateral movement. Golovkin, meanwhile, stuck with single hooks and probing jabs, landing a solid uppercut halfway through the round. In the final 20 seconds, Derevyanchenko landed another body shot which again appeared to hurt Golovkin, who reeled backwards with his elbows down at his side, protecting his body. The sixth was an evenly fought round with both fighters landing several clean punches to the head, although Golovkin appeared to land the more significant blows which caught the attention of the crowd. Rounds seven, eight and nine were much of the same, back and forth engagements with Golovkin seeming to land the more eye catching blows. The tenth saw Derevyanchenko apply the pressure and back Golovkin up for the first half of the round. Golovkin had success in the last minute with left and right hooks landing on Derevyanchenko's head, only to see the Ukrainian answer with his own solid shots and back Golovkin up once again in the final 30 seconds of the round. The eleventh and twelfth were closely contested, both fighters having success, with Golovkin again appearing to land the more catching punches in the twelfth and final round. After twelve hard fought rounds, Golovkin won by unanimous decision with two judges scoring the bout 115–112 and the third scoring it 114–113, all in favour of Golovkin. According to CompuBox stats, Golovkin landed a total of 243 (33.7%) punches out of 720, with 136 (43.3%) of 314 power punches, while Derevyanchenko landed a total of 230 (31.2%) punches out of 738, with 138 (29.3%) out of 472 power punches—the most an opponent has landed on Golovkin to date. In a post fight interview, promoter Eddie Hearn, who lead the promotion of DAZN in the U.S., stated: "...he won't say it, but Gennady has been ill, basically all week", alluding to the reason Golovkin did not appear on top form during the fight.