The Catholic Diocese of Arlington in Virginia said the Rev. William Aitcheson volunteered to take a leave and didn't elaborate on the length of time.
Images of violence in Charlottesville brought back memories of a dark time in his life, one he wishes he could forget but is unable to, Aitcheson wrote this week in The Arlington Catholic Herald
in a piece titled "Moving from hate to love with God's grace."
"While 40 years have passed, I must say this: I'm sorry. To anyone who has been subjected to racism or bigotry, I am sorry. I have no excuse, but I hope you will forgive me," he wrote.
"My actions were despicable. When I think back on burning crosses, a threatening letter, and so on, I feel as though I am speaking of somebody else. It's hard to believe that was me."
Aitcheson, 62, was ordained in 1988 after attending seminary at the North American College in Rome. He spent his early years as a priest in Nevada before becoming a permanent priest of the Diocese of Arlington in 1998.
There have been no accusations of racism or bigotry against Aitcheson during his time at the diocese, it said in a statement.
In his editorial, Aitcheson credits his faith as helping him overcome the hatred he felt as a young man.
"When I left my former life, I did a lot of soul-searching. God humbled me, because I needed to be humbled," he wrote.
"The images from Charlottesville are embarrassing. They embarrass us as a country, but for those who have repented from a damaging and destructive past, the images should bring us to our knees in prayer. Racists have polluted minds, twisted by an ideology that reinforces the false belief that they are superior to others."
Aitcheson's article intended to tell his story of transformation, the diocese said.
"While Fr. Aitcheson's past with the Ku Klux Klan is sad and deeply troubling, I pray that in our current political and social climate his message will reach those who support hate and division, and inspire them to a conversion of heart," Arlington Diocese Bishop Michael F. Burbidge said in the statement.
CNN has reached out to Aitcheson for additional comment.