She was born Floella Karen Yunies Benjamin in Pointe-à-Pierre, Trinidad, one of six siblings, with two brothers and three sisters.
When her father, "a policeman and a talented jazz musician", decided to emigrate to Britain, the children were left in the care of family friends. In 1960 the children went to join him in Beckenham, Kent. She has discussed the racist experiences she had when arriving in Britain as an immigrant.
Having left school to work in a bank, she studied for A-levels at night school. After a spell as a stage actress in West End musicals, she began presenting children's television programmes in 1976, notably Play School for the BBC.
Benjamin has appeared in Hair, Jesus Christ Superstar, The Black Mikado and The Husband-In-Law, as well as several pantomimes. On screen, she appeared in the 1975 horror film I Don't Want to Be Born and starred in the 1977 film Black Joy. Her television credits include Angels, Within These Walls, Crown Court, The Gentle Touch and Dixon of Dock Green. She appeared as Juniper in the first episode of Bergerac (1981).
Benjamin read two stories for the Story Teller magazine series (1983 and 1984). She was chief executive of Floella Benjamin Productions Ltd, which had produced television programmes since 1987 and was dissolved in 2014. She had done the voice work of "U" and "PG" Video Standards Council information clips. In 2006, she appeared in an episode of The Line of Beauty. In 2007–09, and again in 2011, she guest-starred in the Doctor Who spin-off The Sarah Jane Adventures as Professor Rivers from the Pharos Institute in the stories "The Lost Boy", "Day of the Clown", "The Eternity Trap" and "Sky". She narrated three "making-of" documentaries on the Doctor Who DVD box-set The Black Guardian Trilogy. In 2007, she played a small role in the British comedy Run Fatboy Run. She is the singer for a rock and blues band Damn Right I Got The Blues, and says: "When I sing I am in my element."
Her 20th book, a memoir, Coming to England, about moving from Trinidad, was published in 1997, and is now used to teach modern history to young people. Other books written by Floella and published by various houses include titles such as Floella's Fun Book, Why the Agouti Has No Tail, Caribbean Cookery and Snotty and the Rod of Power. Many of her titles are aimed at children and development.
She was appointed an Officer of the Order of the British Empire (OBE) for services to broadcasting in the 2001 New Year Honours. At that time she was chairperson of the British Academy of Film and Television Arts (BAFTA). She has also won a Special Lifetime Achievement award from BAFTA. She was chairperson of the Women of the Year Lunch for five years and a Millennium Commissioner. She is president of the Elizabeth R Commonwealth Broadcasting Fund and a governor of the National Film and Television School. She was a governor of Dulwich College, where her mother once worked and her son attended. She is a Vice-President of the Royal Commonwealth Society.
In 2006, she became an honorary graduate of the University of Exeter and was awarded the degree of Hon D.Litt (Exon) for contributions to the life of the United Kingdom. Lady Benjamin succeeded Lord Alexander of Weedon as Chancellor of the University of Exeter. She famously hugs graduates instead of traditionally shaking their hands during the graduation ceremonies.
In 2008 she was appointed a Deputy Lieutenant of Greater London. In the 2010 Dissolution Honours List she was appointed a Liberal Democrat Life Peer, being created Baroness Benjamin, of Beckenham in the County of Kent on 26 June 2010. In 2010 she was appointed Chair of Governors at The Isle of Sheppey Academy until her term in office expired at the end of 2011.
Benjamin's interest in education has also seen her on the "4Rs Commission" established by the Liberal Democrats to look into primary education in the UK.
Benjamin is vice-president of NCH Action for Children and Barnardo's, and was in the NSPCC's Hall of Fame. She runs the London Marathon to raise funds for Barnardo's and the Sickle Cell Society. She was a cultural ambassador for the 2012 Summer Olympic Games. In September 2011, she participated in the Great North Run. She features in the BBCs CBeebies animation Mama Mirabelle's Home Movies.
In July 2007 she spoke of what she saw as the low standard of children's television and in March 2013, she used a speech marking International Women's Day to warn of the impact on children of the availability of violent pornographic material online, claiming this was leading to the increasing objectification of women.
She is a Patron of the charity Beating Bowel Cancer, having lost her mother to the disease in 2009.
In October 2015 in a talk to migrant children, Floella Benjamin said that dropping her accent was the key to her success and that migrant pupils should do the same to avoid racism and bullying.