The 155-pound, five-round contest will headline a UFC Fight Night, said Abdelaziz, who managers both fighters.
The promotion has not yet announced a location for that event.
"I don't like it when two guys who I really love have to fight, but these two have worked their whole lives to become a champion and this is a No. 1 contender match," Abdelaziz said. "Whoever wins this fight will fight for the title, so who am I to tell them not to fight? They're at the top and I wish both guys the best of luck."
The winner will have a strong case for a lightweight title shot in his next appearance. According to the UFC rankings, Dariush and Makhachev are Nos. 3 and 4, respectively. No. 1-ranked Dustin Poirier will challenge Charles Oliveira for the title in December.
No. 2-ranked Justin Gaethje is also in the title hunt.
In addition to agreeing to the Feb. 26 matchup, both lightweights signed new contract extensions with the UFC, per sources.
Dariush (21-4-1) is riding a seven-fight win streak, including a unanimous decision over former interim champion Tony Ferguson in May. The 32-year-old was born in Iran but now fights out of Huntington Beach, California with Kings MMA.
Makhachev (21-1) has won nine in a row and finished all three of the opponents he faced in 2021. He is a longtime teammate of retired former champion Khabib Nurmagomedov. Nurmagomedov is a regular fixture in Makhachev's corner.