In 1999, development began on the XU30 platform under chief engineer Yukihiro Okane. Design work was started under Makoto Oshima and would continue into 2000 when a concept design by Hiroshi Sukuki was approved. By early 2001, the final production design was green-lighted by the executive board, with the first prototypes being tested in 2002. Design patents were filed on 1 April 2002 under No. 794 at the Japanese Patent Office and on 21 April 2003 at the United States Patent and Trademark Office.[29][30]

The XU30 was previewed in January 2003 at the North American International Auto Show. Featuring a sleeker body style than its predecessor, the XU30 claimed to have a drag coefficient of Cd=0.35 and new LED tailamps.[31][32] From the inside, the RX 330 interior featured genuine Golden Bird's Eye Maple or Walnut wood trim, a sliding multi-level center storage console, dual-zone climate control, and power tilt/telescopic steering column. Available options included a 210-watt, 11-speaker Mark Levinsonpremium sound system, DVD-based navigation system with backup camera, rear seat DVD player with wireless headphones, panoramic three panel moonroof, and heated seats