She began her film career in the late 1940s, and won the Golden Globe Award for Most Promising Newcomer for her performance in That Hagen Girl (1947). Following a number of small film roles, Maxwell became dissatisfied and travelled to Italy, where she worked in film from 1951 to 1955. After her marriage, she moved to the United Kingdom, where she appeared in several television productions.
As Maxwell's career declined, she lived in Canada, Switzerland, and the UK. In 2001, she was diagnosed with bowel cancer and moved to Western Australia, where she lived with her son until her death at age 80 in 2007.
Born in Kitchener, Ontario, to a nurse mother and a teacher father, Maxwell was raised in Toronto and attended Lawrence Park Collegiate Institute. Dissatisfied with the yields of babysitting jobs, she set her sights on something more lucrative and landed her first job working as a waitress at Canada's largest and most luxurious summer resort, Bigwin Inn, on Bigwin Island in Lake of Bays, Ontario.
During World War II, she ran away from home, aged 15, to join the Canadian Women's Army Corps, a unit formed to release men for combat duties. CWAC personnel were secretaries, vehicle drivers and mechanics, who performed every conceivable non-combat duty. Maxwell quickly became part of the Army Show in Canada. Later, as part of the Canadian Auxiliary Services Entertainment Unit, she was posted to the United Kingdom, where she performed music and dance numbers to entertain the troops, often appearing alongside Canadian comedians Wayne and Shuster.
Her true age was discovered when the group reached London. To avoid repatriation to Canada, she was discharged and subsequently enrolled at the Royal Academy of Dramatic Art (RADA), where she became friends with fellow student Roger Moore.
Moving to Hollywood at the age of 20, Maxwell won the actress Golden Globe Award for Most Promising Newcomer for her role in the Shirley Temple comedy That Hagen Girl (1947). In 1949, she participated in a Life magazine photo layout, in which she posed with another up-and-coming actress, Marilyn Monroe. It was at this time that she changed her surname from Hooker to Maxwell, a name borrowed from a ballet dancer friend. The rest of her family also took this name.
Most of Maxwell's work consisted of minor roles in B films. Tiring of Hollywood, she moved back to Europe, living in Rome for five years (1950–55). There she made a series of films, and at one point became an amateur race driver. One of her Italian films was an adaptation of the opera Aida (1953), in which Maxwell played a leading role, lip-synching to another woman's vocals and appearing in several scenes with the still unknown Sophia Loren.
While visiting Paris she met her future husband, TV executive Peter Marriott. They married in 1957 and moved to London, where their daughter Melinda and son Christian were both born (in 1958 and 1959).
Maxwell appeared with Patrick McGoohan in the British TV series Danger Man as his accomplice in the 1959 episode "Position of Trust".
During the 1960s Maxwell appeared in many TV series and in films outside the Bond series in both the UK and Canada, and was the star of Adventures in Rainbow Country in the 1970s.
She also guest-starred in episodes of The Saint and The Persuaders!, both of which starred Roger Moore, and provided the voice of Atlanta for the Supermarionation science-fiction children's series Stingray.
Maxwell had a minor role as a nurse in Stanley Kubrick's Lolita (1962).
In 1963 Maxwell played a machine gun-firing nurse in the series The Avengers (episode "The Little Wonders", which was first aired on 11 January 1964).
In 1965, Maxwell had a guest appearance in "Something for a Rainy Day", an episode of the ITC series The Baron, as an insurance investigator.
Maxwell lobbied for a role in the James Bond film Dr. No (1962), since her husband had suffered a heart attack and they needed the money. Director Terence Young, who had once turned her down on the grounds that she "looked like she smelled of soap", offered her either Miss Moneypenny or Bond's girlfriend, Sylvia Trench, but she was uncomfortable with the idea of a revealing scene outlined in the screenplay. The role as M's secretary guaranteed just two days' work at a rate of £100 per day; Maxwell supplied her own clothes for the filming.
In 1967, Maxwell appeared in the Italian spy spoof Operation Kid Brother with his brother, Neil, and Bernard Lee (who played M). The same year, she portrayed Moneypenny in a made-for-TV special, Welcome to Japan, Mr. Bond, in which she co-starred with Abbe Lane, where the two performed a dance number wearing purple fez and white feathered boas, as well as silver and purple evening gowns created by designer Oleg Cassini.
In 1971, the role of Moneypenny was nearly re-cast after Maxwell demanded a pay raise for Diamonds Are Forever; Moneypenny's undercover policewoman's cap disguises the hair Maxwell had already dyed in preparation for another part. However, she stayed on as Moneypenny when her former classmate, Roger Moore, assumed the role of 007 in Live and Let Die (1973). She reprised her character, weeping for the death of Bond, in a short scene with Lee in the French comedy Bons baisers de Hong Kong (1975).
During the filming of A View to a Kill (1985), her final appearance as Moneypenny, producer Cubby Broccoli pointed out to her that they were the only cast or crew members from Dr. No who had not yet left the series. Maxwell asked that Moneypenny be killed off, but Broccoli re-cast the role instead.
According to author Tom Lisanti, Maxwell's Moneypenny was seen as an "anchor", and her flirtatious relationship with Bond provided the films with dramatic realism and humanism; for Moneypenny, Bond was "unobtainable", freeing the characters to make outrageous sexual double entendres. At the same time, however, her character did little to imbue the series with changing feminist notions.
In 1973, Maxwell's husband died, having never fully recovered from his heart attack in the 1960s. Maxwell subsequently returned to Canada, settling in Fort Erie, Ontario, where she lived on Oakes Drive. She spent her summers at a cottage outside of Espanola, Ontario, where she wrote a column for the Toronto Sun under the pseudonym "Miss Moneypenny" and became a businesswoman working in the textile industry. In 1994, she returned to the UK once again to be nearer to her daughter Daphne, retiring to a cottage in Frome, Somerset.
Following surgery for bowel cancer in 2001, Maxwell moved to Perth, Australia, to live with her son Christian's family. She remained there, working on her autobiography, until her death at Fremantle Hospital on 29 September 2007.
Of his friend's death, Sir Roger Moore said to BBC Radio 5 Live, "It's rather a shock. She was always fun and she was wonderful to be with and was absolutely perfect casting [...] It was a great pity that, after I moved out of Bond, they didn't take her on to continue in the Timothy Dalton films. I think it was a great disappointment to her that she had not been promoted to play M. She would have been a wonderful M."James Bond: Licence to Thrill - TV Movie documentary (1987) as Herself
In Search of James Bond with Jonathan Ross - TV Movie documentary (1995) as Miss Moneypenny
Behind the Scenes with 'Thunderball' - Video documentary (1995) as Herself / Miss Moneypenny
Inside 'Octopussy' - Video documentary short (2000) as Herself
Terence Young: Bond Vivant - documentary video short (2000) as Herself
Inside 'Dr. No' - Video documentary short (2000) as Herself
James Bond: A BAFTA Tribute - TV Movie documentary (2000) as Herself