There were plans to bring Kokoskov back for a second season prior to him being relieved of his duties, according to ESPN's Adrian Wojnarowski.
"After extensive evaluation, I determined it is best to move in a different direction with our head coaching position," Suns general manager James Jones said in a statement. "I want to thank Igor for his work this past season and wish him the best with his future endeavors."
Phoenix reportedly plans on targeting Philadelphia 76ers assistant coach Monty Williams to fill its vacancy. Williams will reportedly meet with the Los Angeles Lakers for a second interview next week to discuss their head coach position.
Williams has ties to Phoenix's front office, having coached Jones during the 2007-08 season as an assistant with the Portland Trail Blazers. He was later hired as New Orleans Pelicans head coach in 2010 by new Suns senior vice president of basketball operations Jeff Bower.
The Suns will also request permission to interview Portland assistant David Vanterpool, sources told The Athletic's Shams Charania.
Kokoskov was hired by the Suns last May, making him the first head coach in NBA history born and raised outside of North America.
Revolving Door in Phoenix
Kokoskov previously worked for the franchise from 2008-13 as an assistant coach. He would go on to serve as an assistant with the Cleveland Cavaliers, Orlando Magic, and Utah Jazz before returning to Phoenix.
The Suns finished the regular season with the worst record in the Western Conference and the second-worst record in the entire Association at 19-63. The team ranked 28th in offense (105.3 points per 100 possessions) and 29th in defense (114.2 points allowed per 100 possessions).