The Honda Civic Si Sedan showcases the performance potential of the Civic. Designed to take on twisty roads like a sports car, it nevertheless provides the everyday practicality of the refined and durable Honda Civic. The 2008 Si Sedan incorporates Honda's Mugen package. This enhances performance as Mugen offers a better suspension, sports car-like enhancements, 18-inch wheels, body cladding, and front and rear spoilers. The bad news is that Honda plans to release only 1,000 Mugen-fitted pieces.

The Honda Civic Si Sedan's 2.0-liter, 16-valve, DOHC engine produces 197 horsepower at 7,800 rpm, and 139 pound-feet of torque at 6,100 rpm. A vehicle stability assist (VSA) system with traction control is standard. The Civic Si Sedan has a unique intake and exhaust tuning, which emphasizes the torque of the K20Z3 engine at low rpm. Thanks to a taut suspension and agile steering, the Civic continues to set a benchmark for quality in the compact car class and is at the top in both performance and value.

The Honda Civic Si sport suspension adds firm spring, damper and stabilizer bar tuning, along with exclusive 17-inch alloy wheels and high-performance tires. Exclusive exterior features include a low-profile rear wing spoiler and Si emblems. The fully-featured Civic Si Sedan interior has a futuristic two-tier instrument panel with quick-reference meter positioning. It includes a rev-limit indicator light and outside temperature gauge. The sports-oriented interior adds specially-bolstered synthetic suede seats with red fabric stitching; and unique trim panels. On the standard Si Sedan, the styling of the rear deck spoiler, cladding and Si badge is distinctive. However, the Si Sedan has the same minus point as other Honda models in this series - restricted head- and legroom.

The Honda Civic Si Sedan's safety system includes Honda's advanced compatibility engineering (ACE) body structure, which enhances frontal collision energy management through a network of load-bearing structures in the front of the vehicle. In addition, the Civic provides a long list of standard safety equipment, including side curtain air bags; front side air bags with a passenger-side occupant position detection system (OPDS); and active front-seat head restraints. To help reduce pedestrian injuries in the event of a collision, the hood and fender areas are designed to crumple on impact.