In February 2001, after operating a successful law practice for more than six (6) years, Mr. Marionneaux became associated with Lewis O. Unglesby at Unglesby Law Firm located in Baton Rouge Louisiana. In February of 2003, the two formed a partnership, known as Unglesby & Marionneaux, LLC, a firm specializing in trial practice.

Mr. Marionneaux has been involved in trying numerous jury trials: both civil and criminal. He is the managing partner of Unglesby & Marionneaux.

Robert M. Marionneaux, Jr., at the age of 27 was elected to the Louisiana House of Representatives. While in the House of Representatives he served on the Criminal Justice Committee which oversees criminal statutes, juvenile justice, the Department of Corrections, and all gaming statutes and regulations. He also served on the Transportation and Agriculture committees.

In 1999, Rep. Marionneaux ran successfully for the Louisiana State Senate and was then reelected in 2003. He is chairman of Judiciary B, the committee which oversees the Criminal Justice system, Juvenile Justice, the Department of Corrections and all gaming related activities. He also serves on Senate and Governmental Affairs, the Revenue and Fiscal Affairs Committee, and the Senate Technology Committee.

Outside of Unglesby & Marionneaux and the Louisiana Legislature, Mr. Marionneaux serves on the Louisiana State Law Institute, an academic think tank which advises the Louisiana Legislature of policy recommendations. He also serves the Louisiana State Bar Assn. As an elected member to the House of Delegates for the 19th Judicial District (2004-2006), he has been recognized and rated by Martindale-Hubbell. He has been rated "BV" which identifies a lawyer with high to very high legal ability, legal expertise and professional stature. He has been a board member and advocate for the mentally challenged by serving on the Louisiana Board of Mental Health. He is also a member of the Louisiana Trial Lawyers Assn.; American Trial Lawyers Assn.; La. Assn. Criminal Defense Lawyers; Louisiana Farm Bureau; and, the Louisiana Cattleman's Assn.; The Million Dollar Advocates Forum (member list).

Upon graduating from Catholic High of Pointe Coupee, Mr. Marionneaux attended Louisiana State University in Baton Rouge, Louisiana, where he received his Bachelor of Science Degree in Criminal Justice, and a minor in psychology and sociology. While attending LSU, he was elected to serve as the Criminal Justice Representative on the General College Student Council. Thereafter he was elected president of The General College, LSU's largest college. On the social scene he was a member of Sigma Nu fraternity.

After completion of his studies at LSU, Mr. Marionneaux enrolled in Southern University Law Center where he was on the Dean's List and represented the Law Center in various capacities. Based on his academic performance he was invited to participate in Law Review. He was also elected Vice President of the Law Center, Southern's first Caucasian student representative

His hobbies include hunting, fishing, snow skiing and working on his cattle farm located in Grosse Tete, Louisiana. He is the father of one child, Robert, and husband of Keely Williams Marionneaux.