Len was born in Antratsyt, Luhansk, Ukraine to a mother named Yuliia, who ran track early in her life.

[6] Len underachieved in his freshman year, averaging 6 points, 5.5 rebounds, and 2.2 blocks per game, but showed lottery pick potential after serving a ten game suspension at the beginning of the year due to NCAA amateurism issues resulting from his play with BC Dnipro, a European club team from his home nation.

Len opened his sophomore season on November 9, 2012, against the reigning champion Kentucky Wildcats, led by ESPN's #1 player of the 2012 recruiting class, Nerlens Noel.

On January 16, 2013, Len scored 10 points, including a game-winning shot with 0.9 seconds in the game, upsetting #14 North Carolina State with a 52–50 win.

On February 16, 2013, Len played a role in Maryland's 83–81 victory over the top ranked Duke Blue Devils.

[8][9] On May 3, 2013, Len ended up getting surgery on his left ankle that resulted in him being out for several months, ultimately causing him to sit out from the 2013 NBA Summer League.

In the Suns' first game of the Summer League, Len recorded 6 points and 6 rebounds against the Golden State Warriors before fracturing his right pinkie finger and was subsequently ruled out until training camp.

[15] On October 7, 2014, a day before the Suns' first pre-season game of 2014 against Brazilian club Flamengo, Len fractured the same pinkie finger again, forcing him to the sidelines once more.

[17] On October 31, 2014, Len recorded his first career double-double with career-highs in points and rebounds with 10 and 11, respectively, in the Suns' 94–89 win over the San Antonio Spurs.

[20] After missing three games due to the injury, he returned to action on February 20 to record 11 points, 10 rebounds and a career-high six blocks in a loss to the Minnesota Timberwolves.

[21] On April 2, he underwent successful surgery to repair his broken nose, an injury he suffered against the Portland Trail Blazers on March 30.

[32] After going 0–4 to start the season, Len helped the Suns record their first win on November 2 with 18 points in a 118–115 overtime victory over the Portland Trail Blazers.

[36] On February 10, 2017, he was suspended one game without pay for leaving the bench area and entering the playing court during an altercation in the Suns' 110–91 loss to the Memphis Grizzlies two days earlier.

On September 25, 2017, after spending the off-season looking to get a better deal,[38] Len signed a one-year, $4.2 million qualifying offer to return to the Suns.

[49] On February 6, 2020, Len and Jabari Parker were traded to the Sacramento Kings in exchange for Dewayne Dedmon and two second round picks.

[6] In August 2018, Len was named to play for the Ukraine national basketball team for the first time at the 2019 FIBA World Cup qualifiers in September.

[63] In December 2015, Len and his mother, Yuliia, created the Len-d A Hand Foundation, a charity that helps reach out to the youth in Phoenix, Arizona and other surrounding areas.