One of six children, he was born in Roebuck in Jefferson County, Alabama, and reared on his family's produce farm. The Amaris grew tomatoes, bell peppers, and eggplants. As a boy, he helped to operate their Huffman Curb Market, which was established when the immediate area became urbanized. He graduated from the former Banks High School, since a middle school. He holds a bachelor's degree from the University of Montevallo in Montevallo in Shelby County, Alabama. He obtained his law degree from the Cumberland School of Law at Samford University in Birmingham.
Amari and his wife, the former Terri Parker, daughter of Charles and Gail Parker, have five children, Katie A. Nero and John, Joseph, Mary, and Emily.
In 1978, Amari was elected as a Democrat to the Alabama House of Representatives from District 34. After one four-year term in the House, he was elected for a one-year term in the Alabama State Senate from District 12. In 1983, he won a special election for the newly established Senate District 15, which he filled until 1999. By 1990, Amari had switched to Republican affiliation and was from 1995 to 1999 the Senate Republican Leader. In 1998, he ran unsuccessfully for the Republican nomination for lieutenant governor. He lost to his state Senate colleague, Steve Windom of Theodore in South Alabama, 178,065 (52.8 percent) to 159,006 (47.2 percent). Windom then barely defeated the Democratic nominee for lieutenant governor, the state Senate President Pro Tempore Dewayne Freeman of Huntsville, 652,465 (50.3 percent) to 644,818 (49.7 percent). In 2002, Amari challenged state Senator Steve French to reclaim the District 15 seat that he had vacated four years earlier to run for lieutenant governor. French easily prevailed with 12,469 votes (60.1 percent) to Amari's 8,274 (39.9 percent).
In 2006, Amari ran unsuccessfully in the Republican primary for the Place 2 seat on the Alabama Public Service Commission, vacated by Democrat-turned-Republican George Wallace, Jr., who ran instead but without success for lieutenant governor. Amari lost the nomination, 58-42 percent, to former state Representative Perry O. Hooper, Jr., of Montgomery, a son of former Chief Justice of the Alabama Supreme Court Perry O. Hooper, Sr. In the 2006 campaign, Hooper called Amari a "RINO, a Republican in name only." Amari replied that Hooper "might have been born in a Republican family, but [by] his conduct ... he has 'left his raising' as they say." Hooper was thereafter defeated in the general election by the Democrat Susan Parker, a former state auditor.
In 2008, Amari defeated an appointed Republican, Norman G. "Norm" Winston, for the civil judgeship of the District 10 Circuit Court, which he still holds.
Amari calls himself "Pro-Life, Pro-Family, and Pro-Business." He was named seven times by his colleagues as "Legislator of the Year". He is a former chairman of the Senate Republican Caucus. He was a delegate pledged to George W. Bush at the 2000 Republican National Convention held in Philadelphia, Pennsylvania.
Amari's son, also named John Amari (born 1981), unsuccessfully sought a seat in the Alabama House of Representatives in 2014, losing in the Republican primary.