The president returned from diplomatic commitments in Israel and Egypt to honor Kirk on what would have been his 32nd birthday.
Kirk, founder of Turning Point USA, was shot dead on September 10 while debating students at Utah Valley University.
Erika Kirk previously shared a stage with President Trump at a memorial event, where she stated she forgave her husband's killer.
Both the House and Senate have approved resolutions to designate October 14 as a “National Day of Remembrance for Charlie Kirk”, with other tributes including potential statues and road renamings.