Among the first to pay tribute was R&B diva Beyonce, who sang "At Last" at President Barack Obama's 2009 inauguration -- prompting a furious James to announce she couldn't stand the younger singer and that she would "get her ass whipped."
"This is a huge loss. Etta James was one of the greatest vocalists of our time. I am so fortunate to have met such a queen. Her musical contributions will last a lifetime," said Beyonce in a statement.
James, who flitted effortlessly from jazz, pop and love ballads to feisty R&B but plunged into drug addiction before resurrecting her career to win six Grammys, died at a hospital in Riverside, California.
She was also renowned for her soulful rendition of such songs as "I'd Rather Go Blind" and "All I Could Do Was Cry."
"Her music defied category. I worked with Etta for over 30 years. She was my friend and I will miss her always," manager Lupe De Leon said in a statement, calling the soulful singer "a true original who could sing it all."
James's husband Artis Mills and son Donto James -- who had been involved in a legal battle over her estate -- were by her side, as was another son, Sametto James, he added.
In tribute to the singer flowers were placed on her star on the storied Hollywood Walk of Fame, the stretch of sidewalk in the tourist heart of Hollywood dedicated to stars past and present.
James, who retired from stage appearances in 2009, lived in Riverside, east of Los Angeles, for the last two decades. She was diagnosed with cancer two years ago.
Her $1 million estate has been the subject of a legal battle between son Donto and husband Mills, who is not his father.
Mills filed a suit last year seeking to have access to his wife's savings account. Donto James resisted the claim on the grounds that his mother gave him him power-of-attorney over her affairs.
A local judge ordered in December that $350,000 be used exclusively for her medical care.
Born Jamesetta Hawkins, James won four Grammys and 17 Blues Music Awards. She was inducted into the Rock & Roll Hall of Fame in 1993 and was awarded a Lifetime Achievement Grammy in 2003.
The LA City Council adjourned its meeting in memory of the star, who began singing as a child in a church in south Los Angeles.
"Her rich voice influenced generations of singers who came after her, from Tina Turner to Bonnie Raitt to Christina Aguilera," said councilwoman Jan Perry.
James infamously launched the attack on Beyonce shortly after the singer -- who played James in the 2008 movie "Cadillac" -- sang "At Last" for the Obamas.
"I tell you that woman (Obama) had singing for him, singing my song, she gonna get her ass whipped. The great Beyonce. Now like I said, she ain't mine. I can't stand Beyonce!" she told a crowd in Seattle the following month.
"She had no business up there singing. Singing on a big ole, big ole president day and going be singing my song that I've been singing forever."
However, in the statement paying tribute to James, Beyonce said: "When she effortlessly opened her mouth, you could hear her pain and triumph. Her deeply emotional way of delivering a song told her story with no filter.
"She was fearless, and had guts. She will be missed."