Jenkins Barnett's Father, George W. Jenkins founded Publix Super Markets. Carol was born in 1956 when Publix was in its heydey. Carol and her five siblings worked at Publix beginning at the age of sixteen. She recalled the time: "The way I grew up, everything was about Publix. We'd go to store openings. I remember attending the 100th store opening when I was eight. I was there for the glory years."

In 1983, Jenkins Barnett joined the Publix Board of Directors and served in that role until 2016. During her time at Publix, the company grew into the largest supermarket chain in Florida, expanded into five other states, and recorded $32.5 billion in sales in 2015.

Publix Super Markets Charities strives to provide the communities it serves with funding for housing with Habitat for Humanity. The charity also supports other causes such as food assistance, education, and youth programs. Since 1991, Jenkins Barnett has served as President of Publix Super Market Charities. Jenkins Barnett helped lead the organization to donate $25 million to nonprofit organizations each year. She helped lead the organization to donate over ten million dollars to Habitat for Humanity.

In 2004, Barnett was presented with the Florida Arts Recognition Award by the Secretary of State of Florida to honor people who support art and culture in Florida. She contributed to many Florida arts organizations, including the Polk Museum of Art, Imperial Symphony Orchestra and Straz Center for the Performing Arts.

In 2011, Florida Southern College announced an undisclosed contribution from Jenkins Barnett in honor of her husband, Barney Barnett, a graduate of Florida Southern. The funds were used to establish the Barney Barnett School of Business and Free Enterprise. The Barnetts also gave a reported ten million dollars to Florida Southern College to establish the Barnett Residential Life Center that was designed by Robert A.M. Stern.

In 2012, the Barnetts were the primary donors to build a $5.5 million, 18-classroom learning facility at All Saints' Academy (Florida) in Winter Haven, Florida. They donated $1 million to the Florida Aquarium in downtown Tampa to help launch the Carol J. and Barney Barnett Learning Center that opened in 2014. In 2015, the Barnetts gave $3 million to Mote Marine Laboratory and Aquarium in Sarasota, Florida to promote environmental conservation. The Barnetts have donated millions of dollars to the United Way.

In 2015, Barnett received the Women in Philanthropy award, a national honor bestowed by the United Way Women’s Leadership Council for her work developing a number of early childhood initiatives, including the ReadingPals literacy program that spread throughout Florida. In 2016, Jenkins Barnett was inducted into the Florida Women's Hall of Fame.

Also in 2016, the Barnetts gave $800,000 to the Drug Free Florida Committee, an organization leading opposition to Amendment 2 to the Constitution of the State of Florida, which legalized marijuana for medical use in Florida.

In 2017, Barnett received the Chiles Advocacy Award, Florida’s highest honor for serving its children. The Barbara Bush Foundation for Family Literacy presented Barnett with its “Champion for Literacy” award. The Barnetts announced plans to introduce the largest park in Lakeland, Florida. Jenkins Barnett has served on the steering committee for The Children's Movement of Florida.

Barnett was named a Notable Member of the Association of Junior Leagues International, an honor given to only 18 women since the association’s founding in 1901.