The star is being presented with the award by the Duke of Cambridge at the event at London's Royal Opera House in Covent Garden.
Dame Helen - who has played the monarch on stage and screen and won the leading actress Oscar in 2007 for The Queen - joins other winners of the prestigious award including Martin Scorsese and Sir Christopher Lee.
She said: "I'll try not to be too emotional about it.
"The emotional quotient, if my lip starts trembling, is the thought that my parents aren't here to be proud and that's the trouble with getting these sort of lifetime things because they do tend to come towards the latter part of your life as opposed to the beginning and they would have been so proud and so pleased for me.
"They would be so relieved that it all worked out".
But the actress said she was not "proud" of her own career, saying: "I look at everything and think 'God you weren't very good in that were you really, Helen?'"
She said she was "grateful" for the role of detective Jane Tennison in gritty TV crime drama, Prime Suspect, because the role taught her "how to act in film".
Asked if she had any regrets over a career spanning almost 50 years, the 68-year-old said: "You can never think that, even with the major disasters you can never think that, because everything you learn on".
Despite her Oscar-winning portrayal of the Queen, Dame Helen said playing a real-life figure is a "poisoned chalice" and she has no plans to play another.
The actress said she had not received feedback from the Royal Family about her performance but hoped the Duke's appearance at the Baftas to present her award indicated they were pleased with it.
Dame Helen was speaking at the Savoy Hotel in central London, where she joined friends and former colleagues for the Hackett Bafta Fellow lunch.
Among the guests at the Bafta Fellow dinner were actor Jeremy Irons and Madness frontman Suggs.
She said: "I'm hoping the fact that William is very kindly being part of the group giving me the award is some indication that I'm not complete persona non grata.
"It's a poisoned chalice really playing a real-life character. I was very lucky because Peter Morgan who wrote both The Queen and the play The Audience is a really superb writer.
"Without that quality of writing, it's a bit pointless really."
It is only fitting that Dame Helen Mirren should be presented with her Bafta Fellowship award by the Duke of Cambridge - as his family has given her some of her finest roles.
The actress acknowledged that herself when she won the leading actress Oscar in 2007 for her performance in the title role of The Queen and dedicated it to Queen Elizabeth II, telling Hollywood: "If it wasn't for her I most certainly wouldn't be here".
It was that most regal of roles that confirmed her as a huge international star.
Before that she had been best known as tough-talking DCI Jane Tennison in Prime Suspect, but she was already an acclaimed stage and screen actress by the time the first instalment of that series was broadcast in 1991.
She was born Ilynea Lydia Mironoff in Leigh-on-Sea, Essex, to a family of Russian aristocrats forced into exile by the 1917 Revolution.
In her youth she once worked at the Kursaal amusement park in Southend as a ''blagger'', to attract customers to the rides.
Mirren decided she wanted to be an actress at the age of six, but went to teacher training college to keep her parents happy.
Eventually she ditched her studies in favour of the stage, and made an immediate impact playing Cleopatra in a 1965 production for the National Youth Theatre.
She was soon snapped up by the Royal Shakespeare Company and tackled numerous classical parts.
In the 1980s she appeared in The Long Good Friday, Excalibur and Peter Greenaway's The Cook, The Thief, His Wife And Her Lover.
Her performances in five Prime Suspects were a huge critical and commercial hit, earning her three consecutive Baftas and an Emmy for the role.
She returned after a seven-year break with Prime Suspect 6 in 2003, and came back again in 2006 for Prime Suspect: The Final Act.
She had been nominated for Oscars twice, in 1995 for The Madness Of King George and for Gosford Park in 2002, before she finally won.
More recent roles have seen her play a retired Israeli Mossad agent in The Debt and the part of Alfred Hitchcock's wire Alma in the 2012 biopic Hitchcock about the making of Psycho.
She also returned to the royal family on stage - playing the Queen again in The Audience which depicts the monarch in conversation with the many prime ministers who have served throughout her reign.
Dame Helen married American producer-director Taylor Hackford in 1997 and the pair divide their time between homes in London and Los Angeles.
The actress, who has backed 12 Years A Slave for Bafta success at tomorrow's awards, said she will return to play the Queen on stage when the West End show The Audience hits Broadway.
The Bafta Awards are being held at the Royal Opera House in Covent Garden, central London, tomorrow. Here are the contenders for the main categories:
:: Best Film
12 Years A Slave
:: Leading Actor
Bruce Dern for Nebraska
Chiwetel Ejiofor for 12 Years A Slave
Christian Bale for American Hustle
Leonardo DiCaprio for The Wolf Of Wall Street
Tom Hanks for Captain Phillips
:: Leading Actress
Amy Adams for American Hustle
Cate Blanchett for Blue Jasmine
Emma Thompson for Saving Mr Banks
Judi Dench for Philomena
Sandra Bullock for Gravity
:: Supporting Actor
Barkhad Abdi for Captain Phillips
Bradley Cooper for American Hustle
Daniel Bruhl for Rush
Matt Damon for Behind The Candelabra
Michael Fassbender for 12 Years A Slave
:: Supporting Actress
Jennifer Lawrence for American Hustle
Julia Roberts for August: Osage County
Lupita Nyong'o for 12 Years A Slave
Oprah Winfrey for The Butler
Sally Hawkins for Blue Jasmine
Steve McQueen for 12 Years A Slave
David O.Russell for American Hustle
Paul Greengrass for Captain Phillips
Alfonso Cuaron for Gravity
Martin Scorsese for The Wolf Of Wall Street
:: Outstanding British Film
Mandela: Long Walk To Freedom
Saving Mr Banks
The Selfish Giant
:: Outstanding Debut by a British writer, director or producer
Colin Carberry and Glenn Patterson for Good Vibrations
Kelly Marcel for Saving Mr Banks
Kieran Evans for Kelly + Victor
Paul Wright and Polly Stokes for For Those In Peril
Scott Graham for Shell
:: Film not in the English language
The Act Of Killing
Blue Is The Warmest Colour
The Great Beauty
Metro Manila Wadjda
The Act Of Killing
The Armstrong Lie
We Steal Secrets: The Story Of Wikileaks
:: Animated Film
Despicable Me 2
:: Original Screenplay
Eric Warren Singer and David O. Russell for American Hustle
Woody Allen for Blue Jasmine
Alfonso and Jonas Cuaron for Gravity
Joel and Ethan Coen for Inside Llewyn Davis
Bob Nelson for Nebraska
:: Adapted Screenplay
John Ridley for 12 Years A Slave
Richard LaGravenese for Behind The Candelabra
Billy Ray for Captain Phillips
Steve Coogan and Jeff Pope for Philomena
Terence Winter for The Wolf Of Wall Street
:: Original Music
Hans Zimmer for 12 Years A Slave
John Williams for The Book Thief
Henry Jackman for Captain Phillips
Steven Price for Gravity
Thomas Newman for Saving Mr Banks