An all-new 6th generation Sonata was launched in August 2004 in Korea. A new platform also was borne out of the project NF for total cost of 290 billion won. The company's first all-aluminum I4 engine, dubbed Theta, debuted in the new Sonata. Engine choices at launch were a 16-valve 2.0 L and a 2.4 L that produces 166 ps at 5,800 rpm.

The U.S. launch of the all-new Sonata kicked off with the historical opening of the first U.S. assembly plant for the Korea-based Hyundai Motor Company in May 2005. The plant is located in Montgomery, Alabama. The Canadian sport version came with an optional 3.3 L Lambda V6 engine with 247 hp and 238 lb•ft of torque. Hyundai claims the car will launch to 62 mph (100 km/h) in 6.7 sec, and have a top speed of 147 mph for the V6. But the car is frequently reported to be going at speeds beyond 160 mph in korea.

The look of the latest model year Sonata resembles a great deal with the Toyota Camry 2007, which is considered its competitor.

The new Sonata is 2 in (50.8 mm) longer and taller and 1 in (25.4 mm) wider than the previous generation. The US EPA now classifies the Sonata as a "large car". It is priced at US$18,500. A V6 Sonata is priced at US$23,500.

The Sonata got the Good Design Award in passenger car category from the JIDPO (Japan Industrial Design Promotion Organization).

The Sonata was named "Best New Family Car (under $35,000)" in the 2006 Canadian Car of the Year awards.