Born in Manchester, Thistleton graduated from the University of Salford with a degree in English and Creative Writing, before qualifying as a NCTJ certified journalist after studying at News Associates, Manchester.
Thistleton previously worked for the NHS Pennine Care Mental Health Trust.
She hosts the CBBC Book Club on the CBBC channel. The Book Club role has seen Thistleton interviewing many leading authors, including David Baddiel, Cressida Cowell, Jeff Kinney, Michael Rosen, Holly Smale, and Jacqueline Wilson.
Thistleton has also appeared on a variety of CBBC shows, including All Over the Place, Blue Peter, Jedward's Big Adventure, The Dog Ate My Homework, and Sam & Mark's Big Friday Wind-Up.
Away from children's television, Thistleton has also appeared on Celebrity Eggheads, Celebrity Mastermind, and Children in Need.
In addition to her televised literary work, Thistleton also hosts author events organised by major publishing houses, including Hachette, HarperCollins, and Penguin.
Thistleton is a regular at literary festivals, including the Edinburgh Literary Festival and Hay Festival. She has also judged The Blue Peter Book Awards and The Royal Society Young People's Book Prize.
Thistleton is passionate about raising mental health awareness. She is an ambassador for mental health charities, Mind and Place2Be.
Since May 2017, Thistleton has hosted BBC Radio 1's The Surgery alongside Doctor Radha Modgil.
Thistleton's debut book—Dear Katie: Real Problems, Real Advice—is due to be published by the Orion Publishing Group in February 2018.