Liverpool City Council's planning committee voted 6-2 to allow the club to add 7,000 seats to the Anfield Road Stand, which currently holds 8,819.
The replacement stand will extend across Anfield Road and near the edge of Stanley Park, drawing an angry response from green campaigners.
The Local Democracy Reporting Service said the council's climate change committee chair, Lena Simic, accused the club of "misleading" the public by not revealing the number of trees until late in the day.
"Do we really want to sacrifice the mature, beautiful trees we have in Stanley Park to this profit-making machine?".
Both club representatives and planning officers said the tree felling was the result of negotiations between the club and the council that had only recently been completed.
Liverpool FC has also agreed to plant 25 new trees on its land and provide the council with enough money to pay for 45 new trees in Stanley Park.
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