Barbara celebrated the occasion with some of her former co-stars from the BBC soap, including June Brown (Dot Branning) and Pam St Clement (Pat Butcher).
The ex-landlady of the Queen Vic joked it was lovely to meet “another small lady”, and was seriously impressed by her “gorgeous skin”.
Barbara was also joined by friends Christopher Biggins and Jane Moore, as well as her husband Scott Mitchell.
According to reports, the orchestra even played the EastEnders theme tune before the Queen arrived at the ceremony.
On receiving the honour, Barbara said: “I am so very honoured, proud and extremely humbled by this honour.
“I feel so lucky to live in a country I love, a job I have always adored which has allowed me to be in a position where I am able to help others.”
Barbara is an ambassador for Age UK and also backs many other charities supporting the elderly, along with launching the British Legion’s Poppy Appeal in October.
The 78 year old was previously made MBE in 2000 and received negative comments when it was announced in December that she would receive her Damehood.
“They start pulling out a whole list of things … that kind of knocks you, saying, 'Why would that go to her, why?’,” she told Sky News.
Barbara has recently returned to the set of the popular soap, as she begins filming her final scenes as Peggy, who will be killed off this year.
When she arrived back on set cast and crew all donned crowns and bowed and curtsied to celebrate her new achievement.
“They all - all of them - had crowns on. All the crew, everybody. Because I was coming here,” Barbara revealed.