"The Greenwood Encyclopedia of Rock History" described it as being "built around soaring guitars, tight vocal harmonies, and "huge" hooks," which were part of the band's appeal. Boston lead singer Brad Delp cited "Peace of Mind" as an example of how Scholz was able to combine the vocal harmonies of the Beach Boys with the heavy guitar sound of Led Zeppelin. "Rolling Stone" commented on how the guitars "feel epic" but also "delicate and intimate." Tom Moon cited "Peace of Mind" and "Long Time" as examples to illustrate how Scholz varied his guitar effects for each "Boston" song, stating that "Peace of Mind" has a "grittier, less airbrushed attack." The song is among the earliest ones in popular music to use vi–IV–I–V chord progression, a variant of I–V–vi–IV progression, widely popular in modern Western music. "Rolling Stone Album Guide" critic Paul Evans called "Peace of Mind" a "satisfying, if similar, followup" to "More Than a Feeling". Scott Tady of "Beaver County Times" described "Peace of Mind" as one of the songs that "helped set the foundation for classic-rock radio." Eric Deggans wrote that "Bouncy, slick tracks such as 'More Than a Feeling' and 'Peace of Mind' defined new parameters for rock radio during the 70s, with soaring vocals searing guitars and trite lyrics." Jamie Reno of "San Diego" magazine described it as an "infectious flick-your Bic staple." MTV's Gil Kaufman similarly described the song as a "rock-radio staple." Brockman called it "one of the most overplayed songs in rock history" but praised Delp's singing, particularly his vulnerability and sincerity, making Brockman believe that Delp really believed the words of the refrain. Gallucci rated it Boston's 5th greatest song, particularly praising the "fuzzy guitar riff" and noting that it has remained a classic rock radio staple. Elliott and Craig both rated it even higher, as Boston's second greatest song behind only "More Than a Feeling." "Guitar World" magazine selected "Peace of Mind" as one of their 50 greatest rock songs of all time. "Peace of Mind" was covered by Stryper on their 2009 "Murder by Pride" album. Tom Scholz also played guitar on that track.