Thunberg used the opportunity on Monday (December 30) to tell the 93-year old Attenborough how his nature documentaries had inspired her.
"You have woken up the world," Attenborough told Thunberg in reply.
The teenager rejoined activists outside the Swedish parliament this month after four months of overseas trips to attend climate conferences in New York and Madrid.
Thunberg came to world attention when she began a grassroots campaign aged 15 by skipping school every Friday to demonstrate outside the Swedish parliament.
The protests have inspired millions of young people to take action against climate change.