Appearance changes for DeVille/Fleetwood included restyled taillamps and a revised front-end look, plus new interior trim. This year's grille had many more horizontal and vertical bars in its simple crosshatch pattern, designed to accentuate the traditional Cadillac front end look. "Cadillac" script returned this year to the wide upper grille bar (driver's side). A thin molding above the grille extended outward, over the headlamps, to wrap around each fender. Quad rectangular headlamps were outboard of twin vertical rectangular parking lamps. The crosshatch grille pattern repeated itself in either side of the license plate. In familiar Cadillac style. Front fenders held large cornering lamps with clear and amber lenses.

Seven new two-tone body color combinations were available for DeVille (and Fleetwood Brougham), with color-coordinated accent striping. New brushed chrome wheel covers showed the Cadillac crest on a black background. Also new: seatbelt chimes, a standard AM/FM stereo radio with digital display, dome light with dual spot map lamps, and optional electrically-controlled outside mirrors. Interiors were upholstered in Durand knit cloth (six colors) or genuine leather. Standard fittings included power door locks and windows, six-way power seat, and automatic climate control.

The standard 425 cu. in. (7.0-liter) V-8 had new EGR riser tubes. A fuel-injected, 195-horsepower version was optional. The Olds-built 350 cu. in. diesel V-8 became optional in mid-year.

Special editions for 1979 included a Custom Phaeton Coupe and Custom Phaeton Sedan, both offering styling touches intended to remind observers of the "classic" convertibles. Features included brushed chrome moldings with flush-mounted opera lamps and the Cadillac crest; reduced-size quarter windows; a sporty convertible-like roof; "Phaeton" script on each rear quarter panel; wire wheel discs; accent striping; 45/55 Dual Comfort front seats with leather seating; and leather-trimmed steering wheel. Phaeton editions came in three color combinations: Cotillion White with dark blue roof and white leather inside; Slate Firemist with black roof and antique state gray leather upholstery; or Western Saddle Firemist with dark brown roof and antique saddle leather seating.

Also on the option list was the DeVille d'Elegance, with new soft Venetian velour upholstery (in choice of four colors) on pillow-style 50/50 seats. It also had Tangier carpeting, special door pull handles, and "DeVille d'Elegance" script on the glove box and exterior. Coupe d'Elegance had opera lamps: sedans had three roof-mounted assist straps. Both bodies had side moldings and accent stripes. Coupe DeVille also came with a Cabriolet roof treatment, including chrome crossover roof molding, in 17 Elk Grain vinyl colors. A French seam surrounded the back window and a Cadillac script and crest identified the Cabriolet model.