Taylforth attended William Tyndale Junior School, Barnsbury Secondary School for Girls, Kingsway College of Further Education and the Anna Scher Theatre School in London. She started her acting career in the 1970s and before securing her big break she worked as a secretary between minor roles. Early television appearances include roles in the BBC comedy Hi-de-Hi!, Shelley, Play for Today, On Safari, Minder, Sink or Swim and The Rag Trade. In 1980, she won the role of Sherry in the film The Long Good Friday, which proved to be extremely successful at the box office.
On 19 February 1985, Taylforth appeared as Kathy Beale in the first episode of the BBC's new soap opera EastEnders. This role earned her huge popularity and public recognition on British television. Taylforth's character was in the show from 1985 until 1998, when she opted to leave. Kathy made 2 guest appearances in 1999 and 2000. During her time on the show, Kathy covered an array of serious issues including rape, domestic violence, teenage pregnancy, divorce, alcoholism and meningitis. She became one of the longest running characters to feature in the soap, but eventually quit in 1998. She made a brief return in 1999 to aid the departure of actor Ross Kemp, who played her character's brother-in-law, Grant Mitchell before leaving again on 6 January 2000.
Although press rumours throughout 2005 suggested that Taylforth was returning to the show, this did not occur and the character of Kathy died off-screen in February 2006, in a car crash in South Africa. Taylforth has commented: "I was a bit upset at first because it was 13 years of my life and I didn't like the thought of being killed off. I thought she might come back to see Ian (her on-screen son) and have some illness. But that's the way it goes." Since, Taylforth has expressed an interest in returning to the show, if Kathy was to 'come back from the dead' and has openly said that it was a mistake to 'kill off' her character. In 2013, she not only repeated her wish to return to EastEnders, but revealed that former producers wanted Kathy back in EastEnders and admitted that it was a very big mistake to kill off the character. However, an EastEnders spokesperson said that producers currently have no plans to bring back Kathy Beale. On 14 November 2014, Taylforth reprised the role of Kathy for a Children In Need special in which Ian knocks his head and sees visions of the deceased women in his life.
On 19 February 2015, Taylforth made a surprise appearance as Kathy Beale, despite the character's apparent death in 2006, in a live segment of the 30th anniversary episode. The BBC then confirmed she would be reprising the role of Kathy permanently. Kathy then made another guest appearance in May before returning in August on a regular basis.
After quitting EastEnders, Taylforth was cast as Jackie Pascoe-Webb in ITV's popular televised drama, Footballers' Wives. In a Channel 4 poll for the 100 Greatest Sexy Moments, a time where she ends up having sex on top of a snooker table with Cristian Solimeno was placed at number 49. She played the role for all five series, which made her the only cast member to appear in every series without taking a break. (Zöe Lucker also appeared in all five series, but left midway through the 4th series before returning towards the end of the final one.) She also appeared on Lily Savage's Blankety Blank in 2001.
In 2006, she played the role of Mandy Searle in the comedy/drama Jane Hall and she also has appeared as a recurring panellist on ITV's topical chat-show Loose Women (2000, 2006 and 2008). She won a regular part in ITV's police drama The Bill playing Sergeant Nikki Wright, and made her first screen appearance on 8 November 2006. Taylforth left the role in 2008.
In January 2013, she became a housemate on the eleventh series of Celebrity Big Brother. She was the fourth person to be evicted from the house after fifteen days.
In February 2013, it was announced that she had joined the cast of British soap opera, Hollyoaks, as matriarch of the Roscoe family, Sandy Roscoe. After just over a year in the role, Taylforth announced her decision to leave the role of Sandy to spend more time with her family. She departed on-screen on 22 August 2014. Taylforth briefly reprised the role of Sandy in December 2014, but she left again shortly afterwards.
Taylforth was partnered with Anton Du Beke in the sixth series of Strictly Come Dancing in 2008, but was voted off in Week 2 after a dance-off with Jodie Kidd. It later emerged that Taylforth had suffered torn knee ligaments whilst in training for the live shows, but chose to dance regardless.
Taylforth is the sister of actress Kim Taylforth. During her time in EastEnders, she dated her fellow castmate Nick Berry, who played Simon Wicks. She began a relationship with Geoff Knights in the late 1980s. The couple lived in Broxbourne, Hertfordshire and later in Arrington, Cambridgeshire. She gave birth to their daughter in 1992. In 1996 she suffered a miscarriage, and less than a year later doctors told her that the baby she was carrying had severe abnormalities and she was advised to terminate the pregnancy." In 1999, she became a mother for a second time.
Knights and Taylforth have an extensive tabloid media history. In January 1994, Taylforth was involved in a high-profile court case when she sued The Sun newspaper for libel after they ran a story claiming she and Knights had performed sexual acts on a slip road on the A1 in their Range Rover. Taylforth claimed that her partner had suffered an acute attack of pancreatitis and she was merely massaging his stomach to soothe his abdominal pain; however, a police officer claimed that she was performing fellatio instead. During the court case, The Sun's defence counsel, George Carman QC, entered into evidence a 35-minute home video of Taylforth "suggestively posing with a large sausage [...] graphically simulating masturbation with a wine bottle" and boasting to the camera, "I give very good head". The incident gave rise to the sarcastic term "Taylforth Sausage".
The jury returned a 10-2 majority verdict in favour of The Sun, after which Taylforth collapsed and was taken away by an ambulance.
In 1995, Taylforth wrote an autobiography entitled Kathy and Me in which she describes her childhood, her teenage years, her first forays into acting and her lifestyle.