Gavin Newsom, leader of the US state most renowned for its progressive environmental policies, pulled out of the visit at the last minute with his wife, citing "family obligations".
However, he said on Wednesday the full reason for the cancellation had been that his four children had "staged an intervention", begging their parents not to go.
“Mom and Dad missing Halloween, for them that was worse than missing Christmas,” Mr Newsom told his former economic adviser Lenny Mendonca during the California Forward economic conference in Monterey.
On Sunday, his wife, Jennifer Siebel Newsom, dropped a hint on Twitter, saying someone who cancels something might be doing something ordinary, such as going out to dinner with their wife or attending a child’s sports’ match.
However, she later deleted that tweet.
“It’s funny how certain folks can’t handle truth,” Ms Siebel Newsom wrote. “Please stop hating and get a life.”
There had been much speculation in the US press about why Mr Newsom did not attend COP26, including claims that he had suffered a reaction to his Covid booster vaccination.
However, he told the conference that he had been trick-or-treating with his children – aged five, eight, ten and 12 – and watched them play in a football tournament.
“It’s been a hell of a couple years for all of us, for each and every one of you, particularly parents,” Mr Newsom added in the interview with Mr Mendonca. “I’ve been on this treadmill. We’ve gone from crisis to crisis.”