Bruce, 65, announced his decision to become a woman during a tell-all interview with ABC's Diane Sawyer and while the show was being broadcast, Humphries took to Twitter to send a vague, message, reported Hollywood Life.
The 30-year-old star posted, "Man, I'm glad I got out when I did. #Gottadoyou."
Subsequently, the basketball player, who was married to Kim from 2011 until 2013, was subjected to a torrent of abuse from online users, many of whom accused him of being insensitive and ignorant.
"I have and always will support Bruce hence #Gottadoyou. Now recognise I was too vague and sincerely apologise for the way this came across. (sic)," Humphries said.
Meanwhile, Bruce's 17-year-old daughter Kylie Jenner has taken to Twitter to declare her support for her dad.
"Woke up still in awe... I've never been more proud of you, Dad! (sic)," she posted.