A Million Ways to Die in the West received mixed reviews from critics. Review aggregation website Rotten Tomatoes gave the film a 33% rating based on 192 reviews, with an average score of 4.9/10. The site's consensus states, "While it offers a few laughs and boasts a talented cast, Seth MacFarlane's overlong, aimless A Million Ways to Die in the West is a disappointingly scattershot affair." Another review aggregation website, Metacritic, gave a score of 44 out of 100, based on 43 critics, indicating "mixed or average reviews". Audiences by CinemaScore gave the film an average grade of "B" on an A+ to F scale; opening weekend demographics were primarily male (55%) and over 25 years of age (72%).
Claudia Puig's review in USA Today was largely positive, writing, "A Western with a contemporary sensibility and dialogue that sounds markedly modern, A Million Ways to Die in the West is quintessential MacFarlane, at once silly and witty, juvenile and clever." Stephen Holden's review in The New York Times was mainly neutral, calling the film "a live-action spinoff of [ Family Guy], with different characters." "While the whole thing feels weirdly miscalculated to me, A Million Ways to Die in the West tweaks the formula just enough, delivers a few laughs and keeps the guest stars coming," wrote Salon columnist Andrew O'Hehir. Rafer Guzman of Newsday found the film amusing, calling it "another example of MacFarlane's ability to mix poop jokes with romance, foul language with sweet sentiment, offensive humor with boyish charm."
In a more negative review, Scott Mendelson of Forbes commended MacFarlane's decision to make an unconventional western comedy, but summarized the film as "just ambitious enough for that to be genuinely disappointing." Michael O'Sullivan at The Washington Post was mixed, deeming the film a "broad, wildly hit-or-miss satire," remarking that he found few of the jokes in the film funny. "Spiritually, it's closer to a mid-range crowd-pleaser such as City Slickers than Blazing Saddles, too enamoured of genre convention to reach for the comic dynamite," wrote Mike McCahill at The Guardian.
Much of the film's criticism was directed towards its writing, running time, and MacFarlane's debut live-action performance. Michael Phillips of the Chicago Tribune criticized MacFarlane's acting and direction as: "A failure of craft. He can't direct action, or even handle scenery well. He can't set up a visual joke properly without resorting to head-butting and bone-crunching, and he doesn't know how, or when, to move his camera. He's not good enough as a romantic lead to anchor a picture." Richard Corliss of Time called the film a "sagebrush comedy whose visual grandeur and appealing actors get polluted by some astonishingly lazy writing." Scott Foundas of Variety found the film "overlong and uninspired," criticizing the film's "lazy writing," and MacFarlane's "surprisingly bland" comic performance.
Rene Rodriguez of the Miami Herald gave the film one star, commenting, "There are enough laughs scattered throughout A Million Ways to Die in the West that while you're watching it, the movie seems like a passable comedy. By the time you get home, though, you can barely remember the jokes." John DeFore of The Hollywood Reporter criticized the film's running time: "Though the film is hardly laugh-free, its uneven jokes appear to have breezed through a very forgiving editing process." Joe Morgenstern of The Wall Street Journal too found the film's length "exhausting," noting, "Some of it sputters, settling for smiles instead of laughs, and much of it flounders while the slapdash script searches [...] for ever more common denominators in toilet humor."