The actor - who plays the title role in The Amazing Spider-Man - appeared in two episodes of the BBC sci-fi drama in 2007.
One of the world's most popular characters is back on the big screen as a new chapter in the Spider-Man legacy is revealed in 'The Amazing Spider-Man'.
"The history of Doctor Who and the heritage and legacy of Doctor Who is huge," Garfield said, in the latest edition of Mark Kermode and Simon Mayo's Film Reviews on BBC Radio 5 live.
"It was an honour to be a part of that show, absolutely. And I'm so happy that everyone is now seeing Matt Smith for the incredible actor and Doctor that he is."
Garfield - who starred alongside Smith's predecessor David Tennant - called the current Doctor Who lead "a friend" and "a tremendous actor".
"I am so proud and happy for him," he said. "He... is being put to fantastic use, and giving so many people so much joy, God bless him. I'm honoured to be a part of that legacy."
The Amazing Spider-Man opens in cinemas on July 3, while Doctor Who is expected to return to BBC One this autumn.
