DeBerry became a candidate for public office in 1972 after becoming disillusioned by her experiences working as a counselor in a federally funded project, where she was one of the few African Americans working with a client population that was almost entirely African American. She was one of five candidates for the state House of Representatives in the 91st District, which had been newly defined by redistricting after the 1970 census. With support from U.S. Representative Harold Ford, Sr., she defeated the four male candidates, and took office in the 88th Tennessee General Assembly that was convened in 1973. She had represented the 91st district from 1973 until her death. As of 2011 she was the longest-serving member of the Tennessee House. In addition to serving on the House committees listed in the following paragraph, she was also Chair of the Special Committee to Study Integration of Ex-Offenders into Mainstream of Society, a member of the Governor's Juvenile Justice Reform Commission, and a member of the Governor's Minority Business Development Advisory Committee. In the 2007-2008 legislative session she served on the House Calendar and Rules Committee; the House Government Operations Committee; the House Health & Human Resources Committee; the House Rules Committee; the House Finance, Ways and Means Committee; the House Ethics Committee; the House Budget Subcommittee; the House Health Care Facilities Subcommittee; the House Public Health and Family Assistance Subcommittee; the House Elections Subcommittee; the Joint Select Committee on Children and Youth; the Joint Select Oversight Committee on Corrections; and the House Committee to Study School Safety Issues. Lois DeBerry worked as an educator. She was President Emeritus of National Black Caucus of State Legislators. She was the first African-American woman elected to serve in the Tennessee House of Representatives from the city of Memphis, the first chairwoman of the Shelby County Delegation, and the first African-American woman to be elected speaker pro tempore of the House of Representatives.
Lois DeBerry co-sponsored a bill in May 2005 that would have required parents to volunteer in schools for at least 12 hours per year. She voted in April 2004 for women to be required to wait 24 hours and receive counseling before having an abortion. She voted against a bill in March 2004 that would have banned civil unions and domestic partnerships in Tennessee. In May 1999, she proposed a bill that restricted credit card companies from soliciting on college and university campuses. She has been a close friend of former Vice President Al Gore for at least 25 years, and she put in his nomination for president at the Democratic National Convention.
Controversies
DeBerry accepted $200 from an undercover FBI agent posing as a businessman during Operation Tennessee Waltz, while celebrating a birthday with fellow Representative Kathryn I. Bowers in 2004. DeBerry defended the decision, saying she did nothing wrong, and that she thought the money was a birthday present. As a result of the incident, she stepped down from the Joint Legislative Committee on Ethics.