"They might have met even much more than just three times," he told NBC News' Keir Simmons in an exclusive interview, dismissing speculation about the leaders' meetings.
"Maybe they went to the toilet together," he joked.
Asked whether the two presidents had other conversations or met in the corridors of the G-20 meeting, Lavrov used the analogy of children mingling at a kindergarten.
"When you are bought by your parents to a kindergarten do you mix with the people who are waiting in the same room to start going to a classroom?" he asked.
Read alsoBBC: Trump and Putin had another, undisclosed conversation at G20He added: "I remember when I was in that position I did spend five or ten minutes in the kindergarten before they brought us to the classroom."
Lavrov echoed the White House account of a third meeting between Trump and Putin during a social-dinner at the summit in Hamburg.
The other two meetings — one a scheduled bilateral meeting and another when the pair shared a handshake — had already been widely reported.
"After the dinner was over…I was not there…President Trump apparently went to pick up his wife and spent some minutes with President Putin…so what?" he said.