The actress, who played Sarah Jane Smith, the sidekick of Jon Pertwee and Tom Baker's time-travelling doctors for a decade, passed away at the age of 63 following a battle with cancer.
Fry has paid his respects to the star, writing on Twitter.com, "What terribly sad news about Elisabeth Sladen - her Sarah Jane was part of my childhood. Deepest sympathy to her family."
And Barrowman, who co-starred with Sladen when she returned to the show in 2006, 'Tweets', "Elisabeth Sladen Matriarch of Dr Who - I loved my time on the Tardis with her. I am proud to have worked with such an icon of the sci fi world. Your Dr Who family are very sad and will miss you and your beautiful smile. (Doctor Who writer) RTD (Russell T. Davies) called me this morning when I woke up. She lived in my flat in Cardiff when she was filming SJA (spin-off series The Sarah Jane Adventures).
"She was a delight. Can't tell you how sad I am. I wanted to let you know I got the news as a lot of you were concerned. I'm off to chill, I hope you understand."