Sir Bernard Hogan-Howe said London had changed in the past 10 years and the Metropolitan Police had "not been able to keep up with that diversity".
This year 79 of the 311 new recruits are BME. In total, 13% of the Met's total police workforce is non-white.
The Met Police Federation said BME officers should also be rising in rank.
The Met said the number of BME (black and minority ethnicity) officers in the force rose from 3,163 in 2013 to 4,033 at the end of August.
It said last year it had a record 28% of new recruits from minority backgrounds, compared to 16% the previous year.
Both Sir Bernard and the mayor have said more needs to be done to improve diversity in the force and will consult lawyers to seek a legal path.
"Targeted recruitment, introducing a London-residency criteria and second-language recruitment campaigns" ensured diversity, the force said.
Sir Bernard said: "The problem in London is that for years two-thirds of the police officers we recruited came from outside London.
"But London changed so much over the last 10 years, a million people arrived, but we have not been able to keep up with that diversity, so what we see now is better recruitment in terms of representation."
London Mayor Sadiq Khan said: "This is not about tokenism but about building trust and respect between our vital police force and all Londoners.
He said the force needed to "look like the communities it is charged with keeping safe".
John Partington, equalities lead officer for the Metropolitan Police Federation, said recruitment was "just the first stage".
"Many will look for promotion and it is important that we do get the right numbers of BME officers at every level and that will make us a truly representative organisation and fit for purpose for London," he said.
London's police are "more representative" of its diversity with the force having 4,033 officers from minorities, the commissioner has said.