John (Nicholas Young, series one to eight) is the leader of the Tomorrow People, and is the only TP to last through all eight series.

Stephen (Peter Vaughan-Clarke, series one to four) is the newest TP, who was introduced in the first story. He is often adventurous and one to take risks.

Carol (Sammie Winmill, series one) was the only female TP in the first series, but Sammie Winmill didn’t renew her contract for the second series. In the story, Carol's absence is attributed to the fact that she is representing Earth in the Galactic Federation.

Elizabeth (Elizabeth Adare, series two to eight) is Carol's replacement. She was a student teacher at Stephen's school, and when she broke out, the term for when a future Tomorrow Person is going through the stage in which he or she acquires their special powers, Stephen and John convinced her to join them.

Mike (Mike Holoway, series four to eight) became a TP after the others found out about him when he was using his powers to open locks, and was involved in a bank break-in. Mike turned out to be good, after all. In addition to being a Tomorrow Person, he is also the drummer in a pop band, the Fresh Hearts.

Ginge (Michael Standing, series one) is a sap1. He was originally a henchman of Jedikiah, a villain, but then changed to the good side, and became a friend and colleague of the Tomorrow People. When Ginge left the show, his character was replaced by Chris (Christopher Chittell), Ginge's brother.

TIM (voiced by Philip Gilbert, series one to eight) is very similar to HAL from the movie 2001: A Space Odyssey. TIM is a biological computer, who is capable of original thought, and does not require special programming. TIM is built into the ceiling of the Tomorrow People's headquarters.

On a few occasions, Philip Gilbert appeared in the series as a live character rather than a disembodied voice. He played Timus and Tikno, clones that became important allies of the TP. One of their other clones provided TIM's speech capabilities, which explains the identical voices of TIM, Timus and Tikno.