Witnessing Kiss live at Madison Square Garden in 1977 made a huge impact on Ian, who has been vocal about his love for the band, and appeared on an episode of Gene Simmons Family Jewels, in which he visited Simmons' home and spoke about the impact Kiss had on his life. Ian went on to be influenced by British heavy metal bands such as Black Sabbath, Iron Maiden, Motörhead and Judas Priest, as well as the punk rock band, the Ramones as an influence. Ian then discovered at the age of 12 that he knew he could become a famous hard rock/heavy metal star. The musical style of his playing and songwriting including fast alternate picking was also largely influenced by the German metal band Accept.

Scott Ian uses his signature Jackson guitars and signature Randall MTS Series heads and cabinets. He is known to use Dimebag Darrell tribute Deans and previously endorsed Washburn. During the mid 1980s, he used ESP guitars for a while, also getting Kirk Hammett his ESP endorsement. Scott uses a DigiTech signature Black 13 distortion pedal, and a DigiTech chorus pedal for his clean sounds. Many of his guitars have been equipped with custom made Seymour Duncan "El Diablo" pickups, but can also be seen using standard Seymour Duncan SH-4's and '59 pickups on several guitars, including his newest signature Jackson. He also recently began endorsing Evertune bridges.

Born Scott Ian Rosenfeld (name has since been legally changed) to a Jewish family in the Bayside section of the New York City borough of Queens, he has a younger brother named Jason (who was involved briefly with Anthrax) and a half-brother named Sean. Scott attended Bayside High School, with classmates (and Future Anthrax bandmates) Dan Lilker and Neil Turbin of the graduating class of 1981.

Ian got into a television gig with VH1 in 2001 when they asked him to host "Rock Show". During his 48 episodes as host, Ian interviewed guests including Ozzy Osbourne, Rob Halford, Ted Nugent, Stone Temple Pilots, Megadeth, 3 Doors Down, Sevendust, Tenacious D and the Cult. Ian is a regular commentator on various VH1 shows including the "I Love The 70s, 80s, and 90s" series, "100 Most Metal Moments", "Awesomely Bad Number One Songs", "When Metallica Ruled The World", and episodes of VH1's "Behind The Music" featuring Metallica, Pantera and Anthrax. Ian was prominently featured in VH1's "History of Heavy Metal". In June 2006, Ian starred in the VH1 reality series "SuperGroup" with Ted Nugent, Sebastian Bach, Jason Bonham and Evan Seinfeld.

In 2008, DC Comics asked Ian to take the character Lobo and write a two-issue prestige format series for that character. Books one and two of Lobo: Highway to Hell were released in November and December 2009.

In late 2009, Ian ended his endorsement with Washburn and went back to Jackson guitars. He was seen using custom made Soloist and Randy Rhoads guitars during the 2009 Sonisphere Festival. On March 27, 2010, Ian announced the production of a new signature guitar by Jackson via Twitter and YouTube. He said it would be based on his Soloist from 1987. It has a silverburst finish, a single Seymour Duncan J.B. humbucker, lightning bolt inlays, and a string-thru/tune-o-matic bridge. A dual-humbucker version with a Floyd Rose tremolo will also be released. He stated, "I am so stoked to be back with Jackson." He was seen using this guitar while playing with Brian Posehn at the Revolver Golden Gods Awards and with The Damned Things at the 2011 Download Festival.

He is a fan of Doctor Who, the television series, as seen in "The Best of the Doctor" that aired August 13, 2011 on BBC America numbered episode 166. Ian is a fan of hip hop music, particularly Public Enemy. He was known to wear Public Enemy shirts while performing gigs in the late 1980s and also said Run-DMC came out with the same aggression that metal bands played with (that he was listening to). He fell in love with rap and said Run-DMC was the group that put rap on the map.

Ian planned a spoken word tour entitled Speaking Words starting in May 2013, in the UK.

In 2014, he joined former members of Mother Superior to form Motor Sister. They released their debut album "Ride" on 9 March 2015.