Caitlin was born in Antrim, Northern Ireland, in 2000. She moved with her family to Inverness in Scotland when she was six years old and has lived there ever since. Blackwood was until recently studying acting in a college based in Edinburgh.

Blackwood played Alexis in the 2015 episode “Preparing the Weapon” of the crowdfunded TV series Cops and Monsters. In 2018 she appeared in a short film called Sundown directed by Ryan Hendrick.

She played the young Amelia Pond in several Doctor Who episodes; “The Eleventh Hour”, “The Big Bang”, “Let’s Kill Hitler”, and “The God Complex”, and a cameo in “The Angels Take Manhattan”. She is the cousin of Karen Gillan, who portrayed the adult Amy Pond, although they had never met before Blackwood was cast. The reason she got the role was due to her physical similarity to her older cousin. In 2018, she starred in Sundown, an award winning short film by Scottish writer and director Ryan Hendrick. In 2020, she played Amy Pond in the Doctor Who short: “The Raggedy Doctor by Amelia Pond”.

At Christmas 2020, she is to appear in the romantic comedy film Perfect Strangers, which also stars Doctor Who actors Sylvester McCoy and Frazer Hines.