Sadiq Khan claimed the top job after beating Conservative Zac Goldsmith, winning 57% of the votes once first and second preferences were counted.
On the Assembly, 12 seats went to Labour, while the Tories now have eight having lost one to Labour.
The Green Party had the third most votes and have two seats in the Assembly, as do UKIP.
The Lib Dems claimed the last remaining seat.
Mr Khan, who becomes the city’s first Muslim mayor, led Mr Goldsmith by 44.2% to 35.6% after first votes were counted.
After second votes were counted, he had 1,310,143 votes compared with Mr Goldsmith’s 994,614. He tally gave him the largest personal mandate of any politician in UK history.
His victory ended eight years of Conservative control of City Hall.
The boroughs taken by Labour are Barnet and Camden, Brent and Harrow, City and East, Ealing and Hillingdon, Enfield and Haringey, Greenwich and Lewisham, Lambeth and Southwark, Merton and Wandsworth and North East.
The Conservatives held Bexley and Bromley, Croydon and Sutton, Havering and Redbridge, South West and West Central.
