The album entered both the Billboard 200 and the Canadian Albums Chart at number four, and gave Beck his first ever Top 10 placing on the UK Albums Chart, peaking at number nine. The album has also been Beck's best charting album in Australia, reaching 13. In the US, the album sold 84,000 copies in its first week. Although successful, this does not match the first week sales of The Information, which were 99,000. In Canada, the album sold over 6,000 copies in its first week.
The album received generally positive reviews upon release, earning a rating of 77 out of 100 on Metacritic.Filter said of the album "Beck is somehow more aware while puffing out his waves of broken poetry as opposed to the casual seed-spitting he has been known to turn to," and Allmusic said that it was "an effective dosage of 21st century paranoia." Some negative reviews, such as PopMatters, said that the album "lacks the unique resonating timbres one is accustomed to with Beck," and The Guardian called it "a vanity project". In December 2008, Modern Guilt was nominated for Best Alternative Album at the 51st Grammy Awards, but it later lost to In Rainbows by Radiohead.
In July through September 2009, Beck uploaded videos on a weekly basis of full band "unplugged" performances of each track on the record. These videos appeared exclusively on beck.com and vimeo.com. These acoustic sessions had been recorded earlier in the year, following Beck's tour of Japan. Four unspecified tracks are to be released on an official limited edition EP.