The model-actress proves to be stiff competition for the Emmy-winning "Mad Men" star.
Ratajkowski, who stars alongside Amy Schumer in upcoming comedy "I Feel Pretty," teamed up with Fallon, while Hamm played with Tarik Trotter, the lead MC of The Roots.
Fallon went up first, having to act out the song, "I Am The Walrus," into which Ratajkowski figured out very quickly. The team began to celebrate, but Hamm reminded them he was not backing down. "You got one point...that was an outsized reaction," he joked.
Next up was Trotter with an impersonation of the movie "The Horse Whisperer," which Hamm answered in even shorter time than his competition.
It became clear at this moment the teams were evenly matched.
The second round was no different, with Fallon quickly guessing Ratajkowski's "Chicken Run," while Trotter figured out Hamm acting out "A Wrinkle in Time."
For the final round, or "Charade Showdown" both Ratajkowski and Hamm went up to act out Beyonce's "Drunk in Love." The Emmy-winning "Mad Men" star went to tackle the third word first, when the model went for the first.
Trotter might be the music man, but Fallon guessed Queen B's hit first. There were no hard feelings, though. "We're all winners!" Hamm yelled, as the whole group jumped up and down while holding hands and cheering.