Dukakis died on Friday night surrounded by her family, her son, John Dukakis, said on Saturday.
She fought to make the world better, "sharing her vulnerabilities to help others face theirs", her family said in a statement.
"She was loving, feisty and fun, and had a keen sensitivity to people from all walks of life," the family said.
"She and our dad, Michael Dukakis, shared an enviable partnership for over 60 years and loved each other deeply."
Dukakis won high marks as a political campaigner during her husband's 1988 presidential efforts, stumping tirelessly for him. She was called a key influence in his decision to seek the presidency.
During the campaign, in 1987, Dukakis revealed she had overcome a 26-year addiction to amphetamines five years earlier after receiving treatment. She said she began taking diet pills at age 19.
Her husband made anti-drug efforts a major issue and she became prominent in the effort to educate youngsters against the perils of drug and alcohol abuse.
But a few months after Michael Dukakis lost the election to Vice President George HW Bush, Kitty Dukakis entered a 60-day treatment program for alcoholism. Several months later she suffered a relapse and was hospitalised after drinking rubbing alcohol.
In her 1990 autobiography, Now You Know, she blamed her mother for much of her alcohol and drug addiction and a long history of low self-esteem.
In 2006, she wrote another book, Shock, which credits the electroconvulsive therapy she began in 2001 for relieving the depression she had suffered for years. The treatment, she wrote, "opened a new reality for me".
Dukakis broke ground by speaking openly about her struggles and championed support for the homeless and political refugees, said Maria Ivanova, director of Northeastern University's Policy School, which hosts the Kitty and Michael Dukakis Center for Urban and Regional Policy.
"Kitty Dukakis brought honesty, compassion, and strength to public life," Ivanova said in a statement. "Her legacy is one of service, resilience, and truth-telling."
Kitty Dukakis inspired many to engage in activism and was a "deeply devoted spiritual companion" to her husband, centre Director Ted Landsmark said in a statement.
"They have been truly effective change-makers on behalf of those in need of care and support," he said.
Dukakis and her future husband met while attending high school in Brookline, Massachusetts, a Boston suburb. He was dull and frugal; she was dramatic and fancy. He is Greek Orthodox; she was Jewish.
Kitty Dukakis, who was divorced and had a three-year-old son, married Michael Dukakis in 1963, and they had two children, Andrea and Kara.
After the presidential election, in 1989, Bush appointed her to be a member of the United States Holocaust Memorial Council.
She earlier served on the President's Commission on the Holocaust in 1979 and on the board of directors of the Refugee Policy Group. She has also been a member of the Task Force on Cambodian Children.
By the late 1990s, Dukakis and her husband divided their time between Massachusetts and California, where she was a social worker and he was a professor for part of the year at the University of California, Los Angeles.
