The actress posted her first tweet on the social networking site last night (April 12), and has already amassed over 45,000 followers.
Gillan posted a photo of herself with Doctor Who co-star Matt Smith in New York City, while they are filming her final episode of the sci-fi series with Arthur Darvill.
"Thanks to everyone following me!!! Argh this is really exciting. Oh, and by the way...WE ARE IN NEW YORK!!!! (sic)," she wrote.
She later joked: "Someone could have told me to turn off my email notifications when i joined twitter today. Plus side? That many cyber friends."
Gillan and Darvill's final episode will occur in the fifth instalment of the upcoming seventh series.
The actress recently said that leaving the show will be a "strange shock to the system".
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Photo gallery - view images from Doctor Who on-location filming in Central Park, New York below: