The Cadillac Coupe de Ville and Sedan de Ville shared a distinctive new interior and exterior appearance as well as a more spacious passenger compartment and increased trunk capacity for 1989. The overall length of the coupe increased 5.8 in. to 202.5 in. while that of the sedan moved up 8.8 in. to 205.2 in. The sedan's wheelbase was also expanded 3.0 in. to 113.8 in. The front overhang of both models increased 2.4 in. to 44.1 in. Their rear overhang was increased 3.4 in. to 47.2 in. New front sheet metal, grille quarter panels and hood were used. A new fascia was used to improve air flow. Both the front and rear bumpers made greater use of chrome and were fitted with an accent-colored rub strip. Bright headlight bezels and cornering lights were also featured along with a rear-mounted power antenna. At the rear a new deck lid, tail lamp and fascia were adopted. Highlighting the 1989 model's profile were new rear wheel "eyebrow" openings and lower body side color accent moldings. The sedan, in addition to having new rear doors had an integrated center high-mounted stop light. If the sedan was ordered with the optional full padded vinyl roof, an electro-luminescent wreath and crest sail ornament was installed.

Beginning with a new seat design with a Primavera cloth trim, numerous interior changes and revisions accompanied the 1989 de Ville's larger and restyled exterior. Many changes were noticeable in the front seat. These consisted of wider headrests, a storage-type center armrest with a flip-open lid and a cup holder option, and manual driver and passenger seat recliners. The sedan's rear compartment had raised rack bolsters with integral headrests, increased lower cushion length for improved thigh support and a reduced corner radius for fuller seat appearance and improved passenger comfort. Three-point shoulder belts were installed along with a raised rear package shelf/storage compartment. The sedan's longer wheelbase provided additional interior space. Rear leg room was increased 3.0 in. to 43.3 in. Knee clearance increased 3.1 in. to 6.1 in. Trunk capacity was increased from 16.1 cu. ft. to 18.4 cu. ft. on the sedan and 18.1 cu. ft. on the coupe. The jack was relocated to a position under the trunk floor which now had a flat surface area. A new trunk trim, Tyger, replaced the Teton material used in 1988. A "Tiffany" carpeting was used for the trunk.

The de Ville models now had new front and rear reversible and washable floor mats with a new retention device. A driver side express-down window was standard as were electrically operated outside car-colored mirrors, front license plate mounting provisions and an AM/FM stereo signal seeking radio with scanner, digital display, cassette player/ five-band graphic equalizer and extended range front speakers. A new Delco/Bose II Symphony sound system was optional as was a digital compact disc player integrated with the Bose II radio. Other new options included an electrochromic automatic day/night rearview mirror with three-position sensitivity switch and a heated windshield. Fifteen inch wheels with Michelin P205/70R15 tires-were standard. Aluminum touring wheels were now available as an option.