The mayor funded the scheme by scrapping The Londoner newsletter
Londoners have been asked to select 10 parks to receive improvement grants of up to £400,000 each.
Mayor Boris Johnson has begun a public vote to select 10 parks from a shortlist of 47. The winners will be made "cleaner, safer and greener".
In addition to the £400,000 award, one park will be given a £2m improvement grant to be chosen by Mr Johnson.
The scheme is being paid for with money saved by the scrapping of the mayor's official newsletter, The Londoner.
Suggested improvements include better footpaths, more lighting, new playgrounds, improved cycle routes and plots for growing fruit and vegetables.
Shortlisted parks include Brent River Park in north London, Victoria Park in east London, south London's Penge Park and Hammersmith Park in west London.
Mr Johnson said: "Parks provide a free place for families to enjoy time out and often simple improvements such as better play areas and improved lighting can make a real difference in making parks much more attractive and safer for people to use."
The grants will be delivered over four years. Voting ends on 30 January.
However, the London Assembly's Labour group is unimpressed with the project and has accused Mr Johnson of cutting more than £400,000 from the environment budget.
Labour environment spokesman Murad Qureshi said: "On the very same day Boris tries to reinvent himself as pro-green and pro-environment, the reality at City Hall is true blue.
"He has decimated the environmental department and slashed their budget."
Mr Qureshi said the mayor was cutting 10% of staff in the department, as well as trimming several programmes aimed at protecting the environment.