Westminster councillors voted three to one in favour of granting planning permission for the Garden Bridge on Tuesday night.
Devised by Joanna Lumley, designed by Thomas Heatherwick and landscaped by Dan Pearson, the Garden Bridge would link the South Bank with Temple Underground Station.
Less than a month since Lambeth councillors resolved to grant planning permission for the southern part of the Garden Bridge, Westminster has done likewise.
Committee chair and deputy council leader Robert Davis said that he had always been a fan of Heatherwick and the bridge will be a "fantastic, superb addition to our historic city" with "substantial and significant public benefits".
His Conservative colleague Cllr Tim Mitchell added: "We're approving a new icon for London".
Cllr Susie Burbridge (Conservative) had some misgivings about the bridge and was concerned that the maintenance burden might fall on Westminster Council if the Garden Bridge Trust collapses.
However she concluded: "I love innovation, I love ideas, and this is one of them".
Labour's Cllr David Boothroyd was the only committee member to vote against the scheme, citing the bridge's "limited" transport benefits and its impact on views from Waterloo Bridge and the South Bank.
Westminster Council has imposed a condition on its proposed grant of planning permission that the Garden Bridge Trust must provide suitable surety or guarantee that future maintenance costs can be met before work on the river crossing can begin.