"Divorce can be a trying, draining, and emotionally devastating experience for all involved," the Hills villain told People. "Despite these hardships, most individuals manage to conduct themselves with dignity and maturity."
Pratt, 27, said he plans to do some "intense soul-searching" following his actions after the couple's split.
"I horribly embarrassed the one person that meant the world to me. For my outrageous and infantile behavior, I offer Heidi my most sincere apologies," he said. "She never deserved the pain and anguish I put her through, and although I don't expect it, I hope in time she'll be able to forgive me."
Montag, 23, filed for divorce in July after one year of marriage.
An e-mail to Pratt's rep was not immediately returned.
Do you think Pratt's apology is sincere?