The critical reaction to La Cousine Bette was immediate and positive, which Balzac did not expect. Whether due to the intensity of its creation or the tumult of his personal life, the author was surprised by the praise he received. He wrote: "I did not realize how good La Cousine Bette is ... There is an immense reaction in my favour. I have won!" The collected edition sold consistently well, and was reprinted nineteen times before the turn of the 20th century. 20th-century critics remain enthusiastic in their praise for the novel; Saintsbury insists it is "beyond all question one of the very greatest of [Balzac's] works". Biographer Graham Robb calls La Cousine Bette "the masterpiece of his premature old age".
Some 19th-century critics attacked the book, on the grounds that it normalized vice and corrupt living. Chief among these were disciples of the utopian theorist Charles Fourier; they disapproved of the "immorality" inherent in the novel's bleak resolution. Critics like Alfred Nettement and Eugène Marron declared that Balzac's sympathy lay with Baron Hulot and Valérie Marneffe. They lambasted him for not commenting more on the characters' degenerate behavior – the same stylistic choice later celebrated by naturalist writers Émile Zola and Hippolyte Taine.
Balzac's novel has been adapted several times for the screen. The first was in 1927, when French filmmaker Max DeRieux directed Alice Tissot in the title role. Margaret Tyzack played the role of Bette in the five part serial Cousin Bette made in 1971 by the BBC, which also starred Helen Mirren as Valérie Marneffe. The film Cousin Bette was released in 1998, directed by Des McAnuff. Jessica Lange starred in the title role, joined by Bob Hoskins as Crevel, and Elisabeth Shue as the singer Jenny Cadine. Screenwriters Lynn Siefert and Susan Tarr changed the story significantly, and eliminated Valérie. The 1998 film was panned by critics for its generally poor acting and awkward dialogue. Stephen Holden of the New York Times commented that the movie "treats the novel as a thoroughly modern social comedy peopled with raging narcissists, opportunists and flat-out fools". The 1998 film changed the novel quite drastically, retaining the basic idea of Bette avenging herself on her enemies, and not only eliminating Valerie, but letting Bette survive at the end.
La Cousine Bette was adapted for the stage by Jeffrey Hatcher, best known for his screenplay Stage Beauty (based on his stage play Compleat Female Stage Beauty). The Antaeus Company in North Hollywood produced a workshop in 2008 and presented the world premiere of Cousin Bette in early 2010 in North Hollywood, California. The adaptation retains many of the main characters but places Bette as the story's narrator.