MacKaye has contributed to several books, including The Idealist by Glen E. Friedman (Burning Flags Press, 1998, updated 2004, ISBN 0-9641916-5-2), a foreword to indie-punk band Photographer Pat Graham's photobook Silent Pictures, an introduction to Susie Horgan's photobook Punk Love, Interrobang?! Anthology on Music and Family, edited by Sharon Cheslow and is interviewed in American Heretics: Rebel Voices In Music by Ben Myers (Codex Books, 2002). MacKaye is also featured in the Friedman book Keep Your Eyes Open (ISBN 0-9641916-8-7), a collection of Fugazi photos taken by Friedman over the course of the band's career.

Ian MacKaye was born in Washington D.C. on April 16, 1962, and grew up in the Glover Park neighborhood of Washington D.C. His father was a Writer for the Washington Post, first as a White House reporter, then as a religion specialist; the senior MacKaye remains active with the socially progressive St. Stephen's Episcopal Church. In his capacities as a Journalist in the White House Press Corps, MacKaye's father was in the presidential motorcade when John F. Kennedy was killed in 1963. Ian Mackaye's Grandmother on his fathers side was Dorothy Cameron Disney Mackaye. She worked with Paul Popenoe on marriage advice columns . She was a member of the Cosmopolitan Club. His Grandfather was Milton MacKaye, also a magazine Writer, and he was an executive with the Office of War Information. According to MacKaye's longtime friend, singer Henry Rollins, MacKaye's parents "raised their kids in a tolerant, super-intellectual, open-minded atmosphere."

Ian MacKaye's next project, The Teen Idles, he played bass guitar and sang back up vocals in from 1979–1980, and the short-lived Skewbald/Grand Union (1981–1982).

Ian MacKaye has been a strong proponent of the Riot Grrrl movement, going as far as to produce Bikini Kill's self-titled EP. Because of the male dominated tendencies of punk concerts during the 1980s, he feels women were pushed away from the movement. He has discussed gender inequalities in some of his songs such as Fugazi's "Suggestion". Despite being a supporter of Riot Grrrl, he came under criticism by those within the movement who claimed MacKaye was simply capitalizing on gender inequality for ulterior motives and that it was not his position to be a part of Riot Grrrl. MacKaye dismissed these claims as unfounded and ignorant. Arguing the success of the movement, MacKaye mentions that he used to note the oddity of a woman playing in a band, but now it has become a normality.

The song "Straight Edge" was written by MacKaye for his band, Minor Threat and was released in 1981 on Minor Threat's self-titled EP. It was a song that described his personal life free of the drugs and the self-destructive idea of "sex as a conquest" which served as a part of the "sex, drugs and rock'n roll" banner originating as a rebellion in the 1960s – smoking, drinking, and drug use. The song came about through MacKaye witnessing his friends abusing alcohol/drugs and acting recklessly. He decided early on that it was not the lifestyle for him, having never fit in with it. MacKaye's main goal was to fight against the people around him who abused substances. His decision to abstain from substances began to influence youth culture as Minor Threat gained popularity through numerous live shows and sales of their EP. Although to MacKaye the song did not represent a philosophy or a movement, over time people adopted the philosophy of the song and many bands began to label themselves straight edge, founding the straight edge movement. Although straight edge is not explicitly supportive of vegetarianism, MacKaye has stated that he is a vegetarian because he regards it as a logical progression of his views. He follows a strict vegan diet. In interviews especially in his later life, MacKaye has often become annoyed with questions about being the founding father of a movement he never intended to start. "I'm credited because I coined a phrase and wrote a song about it. I'm not going to spend any more Energy than I already have explaining that. From the very beginning I've tried to say that this is not my opinion. That whole thing just makes me realize I don't have any control over what people think of me. And I don't really give a fuck. I think that the idea of straight edge, the song that I wrote, and the way people have related it, there's some people who have abused it, they've allowed their fundamentalism to interfere with the real message, which in my mind, was that people should be allowed to live their lives the way they want to. It was just the title of a song that I wrote but certainly never intended to start a movement."

In 1982, MacKaye sang lead vocals on one version of a Government Issue song titled "Asshole". The previously unreleased track was featured on the 20 Years of Dischord collection released in 2002. Backing vocals and collaborations – as, for Example, with brother Alec MacKaye's former band Ignition – are numerous.

After Minor Threat broke up, MacKaye was active with several relatively short-lived groups, including Embrace (1985–1986) and Egg Hunt (1986). Pailhead (1987–1988), a collaboration between MacKaye and the industrial metal band Ministry, then consisting of Al Jourgensen, Paul Barker, and william Rieflin, featured MacKaye on lead vocals.

In 1987, MacKaye founded Fugazi, a band that has been cited as one of the most important post-hardcore groups. Fugazi set itself apart from most other bands by never playing a show with high-priced tickets. They would often turn down venue options for this very rule, and the band would go so far as to stop a show and have unruly concert goers escorted out of the venue – complete with a refund of their ticket money. The band famously turned down at least one offer to headline Lollapalooza because festival organizers refused to price tickets cheaply; MacKaye disagreed with a $30 ticket price. MacKaye also has never conducted an interview with Rolling Stone magazine or any other similar publication, stating he'd only do so if the magazine agreed to not advertise cigarettes or alcohol. MacKaye estimates that for every concert Fugazi played, they turned down another 50 venue options. Fugazi were active until 2003 and have since been on an indefinite hiatus.

In 1988, he recorded vocals with Ministry's Al Jourgensen, Paul Barker, and Bill Rieflin for the band Pailhead's EP titled "Trait". He also co-wrote the song "I Will Refuse" which was also released by the Wax Trax! record label.

MacKaye contributed an extra guitar track to "Youth Against Fascism", the second single from Sonic Youth's 1992 album Dirty.

In February 2004, MacKaye produced the recording sessions for John Frusciante's solo album titled DC EP. After working with MacKaye, Frusciante states "Ian is one of the only living people who I really respect and look up to, so it was an honor and a pleasure as well as a great learning experience to hear his perspective."

MacKaye has also contributed guitar and backing vocals to Joe Lally's solo albums There to Here, released in October 2006, and Nothing Is Underrated, released in November 2007.

In 2007 MacKaye provided technical audio assistance to Alan Canfora, a former Kent State University student who, in 1970, was injured by a gunshot while protesting the U.S. invasion of Cambodia. MacKaye cleaned up a field recording of the incident made by another student named Terry Strubbe. According to Canfora, a voice can be heard on the tape yelling, "Right here! Get set! Point! Fire!" before a 13-second volley of gunfire commences.

Despite persistently voting Democratic, MacKaye does not explicitly consider himself a Democrat. He has explained that he votes solely for the Politician least likely to engage in war. He also noted that he had voted for Obama in the 2008 presidential election. When further probed for a summation of his political views, he explained:

He has been close friends with Henry Rollins since childhood and was the first person to take the stage at Rollins' 50th birthday performance at the National Geographic Explorers' Hall in Washington DC on February 13, 2011. They speak to each other every week by phone, usually on Sundays.

In 2012, MacKaye's wife threw him a surprise 50th birthday party which included many guests from the late 1970s and early 1980s DC punk/hardcore scene, many of whom hadn't seen each other in 20 years.

Throughout his career, MacKaye has opted to advertise in independent and underground media and perform in unconventional venues. Such practices keep admission prices low (in the $5–$15 range) and allow fans of all ages to attend performances. Maintaining a low overhead and protecting monetary assets are also important ideals for MacKaye, who in the summer of 1990 formed the corporation Lunar Atrocities Ltd in order to shield his own and his bandmates' personal assets from the threat of lawsuits. As Seth Martin, MacKaye's financial adviser explained to the Washington Post in a 1993 interview: "protection from liability is the main reason to form a corporation, and for these guys it makes sense. If someone got hurt stage-diving and decided to sue, it would be a little harder to go after their personal assets."

MacKaye was interviewed in the documentary films Roll Up Your Sleeves, DIY America, American Hardcore, 930 F, Another State of Mind, Instrument, Dogtown and Z-Boys, D.I.Y. or Die: How to Survive as an Independent Artist, Don't Need You: The Herstory of Riot Grrrl, Punk's Not Dead, We Jam Econo, I Need That Record, EDGE: Perspectives on Drug Free Culture, Salad Days and the K Records documentary The Shield Around the K. In 2014, MacKaye was featured in the documentary Foo Fighters Sonic Highways which follows and celebrates the Foo Fighters on their 20th anniversary, and the making of their 8th studio album Sonic Highways. The documentary revisits the band's sources of inspiration where MacKaye, among others, have played a defining role. He was also interviewed in the documentary film Breadcrumb Trail, made about the band Slint