Police have stepped up patrols in response to the attack in Orlando which left 49 people dead inside a gay nightclub, and are reviewing their policing of Pride in London.
"Prime locations" are seeing patrols stepped up, with police visiting gay clubs offering reassurance.
They say they have a "robust" policing plan for the annual Pride in London on June 25 in central London, but "there are a number of contingencies in place that will be reviewed".
The attacks at the Pulse nightclub on Sunday also left 53 people injured.
City Hall say an estimated 20,000 people attended a vigil in Old Compton Street on Monday to pay tribute to the victims.
The gunman Omar Mateen died at the scene of the attack.