"In the 30-odd years of my career I've had many, many occasions where I've been in company with Barbara - or, as everyone just called her, "Babs" - and she will be sorely missed", the British-American actor said.
'I spotted her one day and said to Scott, "That's Amy out there having a cigarette, you should go out",' Barbara told the Daily Mirror in 2012.
He continued: "It was not the ending that Barbara or anyone else living with this very cruel disease deserve".
Her death was announced by her husband Scott Mitchell.
Mitchell said her death was hard, but she had showed courage and helped spread awareness of Alzheimer's/Dementia.
Born in Shoreditch in 1937, she had made her West End debut by the age of 15. "We were like family for a long time, ups downs, ins and outs but you will never meet a more professional actress than Babs". Hard it was, but I have been happy since I left and we have had a great life.
Scott Mitchell was Dame Barbara Windsor's third husband, having previously Wednesday Ronnie Knight between 1964 and 1985, and Stephen Hollings between 1986 and 1995. I hope it'll ring in my ears forever.
A year later, the TV star delivered a letter, signed by 100,000 people, to Boris Johnson.
He tweeted: "Ah, #BarbaraWindsor was so very, very lovely".
Barbara and Stephen were granted their divorce in 1995 and, five years later in 2000, the former EastEnders actress married Scott.
David Walliams, Lucas' Little Britain co-star, said Dame Barbara was the "unofficial Queen of England, an icon for over half a century and treasured by the nation". "She was a remarkable woman and it's not an overstatement to say I think the whole country is in mourning today".
"Coronation Street" actress Jane Danson (Leanne Battersby) was "absolutely made up" when she met Barbara in 1998.
He added that she knew how to carry herself on set, saying: "You know what it means to be the top of the bill, to have the responsibility of carrying the show and and looking after everybody that's all around you, helping you to move it along and keep it up to scratch, and she had to do it".
The Carry On star also dated Charlie Kray, the brother of gangster twins Ronnie and Reggie.
Dame Floella Benjamin and singer Aled Jones both remembered the star as a "national treasure" in tweets.
One wrote: "I saw Barbara Windsor make a personal appearance at Heaven's G-A-Y in the late 80s, camping up her famous bikini scene..."