When the Japanese attacked Pearl Harbor on 7 December 1941, Arkansas was stationed in the Atlantic fleet and anchored in Casco Bay, Maine. Beginning in early 1942, Arkansas assignment was convoy escort in the Atlantic Ocean between the US east coast to the European theater. At Norfolk Navy Yard, Virginia, Arkansas underwent an extensive refit between 6 March and 26 July 1942. Four remaining 5in/51cal located on the gun deck were removed and plated over, leaving only six out of her original 21 5in guns. She also received a tripod foremast. After refit, she spent about four months as a training ship for midshipmen. With this completed, she again returned to escort duty until April 1944. Between December 1941 to April 1944 she made a total of eight trips across the Atlantic as a convoy escort.

In late April 1944, Arkansas prepared for her shore bombardment role for the invasion of Europe at Normandy, France. During the invasion, Arkansas, along with the battleship Texas, was to provide fire support at Omaha Beach, while Nevada was at Utah Beach. On D-Day (6 June 1944), Arkansas was stationed about 4000 yards off Omaha Beach and commenced firing at 0552. The three battleships continued to provide fire support until the fighting moved too far inland for the big guns to accurately reach. With this job done, the three battleships moved off Cherbourg, France, where they engaged German shore batteries on 25 June 1944. While there were several close calls, the German batteries failed to hit Arkansas and Cherbourg was successfully captured the following day. The following month, she operated in the Mediterranean and again provided fire support for the invasion of southern France at Toulon between 15 to 17 August as part of Task Force 87.

Strong footholds in Europe meant that Arkansas was no longer in much need so she prepared to transfer to the Pacific Ocean. Prior to the journey, she again had a major refit between 14 September to 7 November 1944 at Boston Navy Yard. Here she received some superstructure modifications and changes in secondary and light guns. Among these included the addition of a pair of additional 3" guns and some quad 40mm guns on the fantail. On 10 November 1944, she begain her journey to the Pacific via the Panama Canal. After spending about a month operating on the west coast, Arkansas sailed for Pearl Harbor on 20 January 1945. Soon after, she sailed to Ulithi and then to Tinian on 12 February.

Arkansas was again used for shore bombardment for the invasion of Iwo Jima. Shelling commenced at 0600 on 16 February and continued to the evening of 19 February. She left Iwo Jima for Ulithi again on 7 March in order to prepare for her next role at Okinawa, the last major amphibious invasion of the war. The shelling of Okinawa commenced on 25 March 1945 almost a week before the 1 April land invasion. Arkansas continued bombarding Okinawa for 46 days and in the meantime defending against large forces of kamikaze aircraft. By mid May 1945, Arkansas was in drydock at Apra Harbor, Guam, and then sailed to Leyte Gulf in the Phillipines on 12 June where she remained until the war ended in August.

With her career at an end, Arkansas transported troops back to US throughout the remainder of 1945. On 25 July 1946, she was used as a target ship and sunk in Operation Crossroads, the atomic bomb tests at Bikini Atoll, where she was located near ground zero of 'Baker Test.' She was awarded four battle stars for her service in World War II.