"It was special, a special time for 'Z,' and I'm happy I was able to be a part of it," the four-time MVP said before Sunday's game against the Bulls in Chicago.
James spent thousands to charter a plane for the ceremony and kept a rather low profile, staying close to the Cavaliers' bench and taking pictures with his phone. It was a surreal sight, given the circumstances surrounding his departure to Miami four years ago -- his decision and owner Dan Gilbert's infuriated letter in response.
James' relationship with the organization has improved in recent years, with former general manager Chris Grant doing all he could to mend it on both sides before getting fired a month ago. And with Ilgauskas being honored, James wanted to be there.
"He was one constant teammate I had over the years, one constant friend that I had as far as this profession," he said. "You can't really get those times back. I felt like for me to be there for eight of his years, being a good friend, there was no way I was going to miss it if I had an opportunity to [attend]."
James was invited to the ceremony by Ilgauskas, with whom he played seven seasons with in Cleveland and one in Miami.
Earlier Saturday, James posted a tribute to Ilgauskas on his Instagram account, writing "words can't express how happy I am" for his former teammate.
Ilgauskas was equally happy to have James there.
"There was some talk leading up to everything. The way I looked at it, if he wasn't able to make it, that's OK. I wanted to extend the invitation," he said, according to the (Cleveland) Plain-Dealer.
"But him being here is an added bonus for me because of what we've been through together. I consider him a dear friend, and we played so much, achieved so much, failed many times but also were successful a lot of times. For me, it would have been almost a detraction if he wasn't here. Now that he was able to witness that made it so much more special," he said, according to the newspaper.
Ilgauskas conquered career-threatening foot injuries to become a two-time NBA All-Star as well as the Cavs' career leader in rebounds (5,904), games played (771) and blocks (1,269). He's second on the scoring list, behind only James.
"Probably one of the most talented guys I ever played with," James said Saturday.
The 7-foot-3 Ilgauskas became the seventh player in team history to have his jersey retired, joining Austin Carr, Nate Thurmond, Bobby "Bingo" Smith, Larry Nance, Brad Daugherty and Mark Price.
Ilgauskas thanked everyone he could during his speech.
"Thank you for not giving up on a skinny kid from Lithuania," he said to Gund.
Later, he saluted Cleveland fans.
"Thanks for giving me a place I can proudly call home," said Ilgauskas, who recently became a U.S. citizen.
Moments later, his jersey was raised slowly toward the ceiling as U2's "Beautiful Day" filled the sold-out arena.
Ilgauskas spent 12 seasons with the Cavs, and for a long stretch of his tenure he was the only good thing about the franchise. That all changed when James arrived in 2003, and along with Ilgauskas -- an odd couple if there ever was one -- they led the Cavs to their only NBA Finals appearance in 2007.
One of the enduring moments in Cleveland sports over the last 30 years was James and Ilgauskas wrapping their arms around each other to celebrate the Cavs' win over Detroit in the Eastern Conference finals. After being traded, Ilgauskas followed James to Miami and played one season with the Heat.
Ilgauskas retired in 2011, but returned to the Cavs the following year and has been working as a special assistant to the general manager.
Information from the Associated Press was used in this report.