The Mayor of London said the subject should be put on the curriculum as a key language option in the way pupils are currently offered French or German.
He suggested that learning the Chinese language while young would help give pupils a competitive advantage.
Mr Johnson, who revealed he is learning the language himself, said: "I certainly think that it would be a good thing if it was more widely available. We wouldn't really be exploiting our relationship with China to the full until children were taking it up in a much bigger way.
"We're going to need our kids to know Mandarin on a much more frequent and regular basis."
He added: "My kids are learning Mandarin. Generally the study of modern languages in our schools is very sadly neglected.
"If you look at what's happening to French and German they have both been declining. Mandarin seems to be the classic example of one that needs to be accelerated."