Tarver took part in the only season of the reality television program American Juniors. Competing against thousands of others who auditioned for the show, she succeeded in making it to the finals (top ten), but did not win a spot on the five member band.
On June 14, 2011 Katelyn released her EP "A Little More Free" independently and began a tour with Honor Society (band) as an opening act on the "Wherever You Are Tour" from June- July 2011.
Using motion capture Tarver acted as the title character in the direct-to-video movie The Barbie Diaries, released in 2006. Sensors recorded her movement, so her movements would control the movement of the animated figure of Mattel's Barbie.
She also starred played the lead role in Mitchel Musso's single The In-Crowd and is featured on the duet "Us Against The World" on Mitchel Musso's album. This opportunity came as she was in the studio working on a track entitled Fastlane when Mitchel came early to his session. When it was Mitchel's turn to record he finished the song and his dad Sam suggested trying it as a duet and since Katelyn was there, she was the obvious choice. She also starred as a contestant on a new reality web show called Miller Production. She stayed on season 1.
Big Time Rush
On January 29, 2010, she made her acting debut on Big Time Rush as Jo, a girl which the boys have a crush on. Her first episode was "Big Time Love Song" which aired on February 5, 2010. She began to have feelings for Kendall Knight (Kendall Schmidt) and after a while, they start dating. But everything had changed since the worldwide tour started; Jo became a famous TV star and Kendall is a pop star. On the episode "Big Time Break-Up" she gets a role in a movie in New Zealand and will be there overseas and can't see Kendall for three years, it aired on 6-25-11.
No Ordinary Family
From 2010 to 2011, Tarver had a recurring role as Natalie on the ABC series No Ordinary Family, appearing in five episodes.