After graduating from Brooklyn College with a music degree in 1970, he was a member of rock/country/jazz band Brethren with Rick Marotta, Tom Cosgrove and Stu Woods.

Garson worked with the reformed Spiders from Mars in 1975, alongside Mick Woodmansey, Trevor Bolder, Dave Black (guitar) and Pete McDonald (vocals).

The latter album included the recording debut of Jessica L. Tivens, at age 13, who had previously appeared on the American television show Star Search.

After the tour, he joined The Smashing Pumpkins guitarist Billy Corgan on his solo effort—the soundtrack for the 1999 supernatural horror film Stigmata.

Additionally Garson played piano on The Smashing Pumpkins next 2000 album Machina/The Machines of God on the songs "Glass and the Ghost Children" and "With Every Light".

[7] Garson played piano on the songs "This is the Life for Me" and "Washed Out to Sea" from Something for Kate's 2006 album Desert Lights.

Garson also contributed to and received co writing credit on the track "Something Unseen" by Athens, Georgia, based power pop band Chris McKay & the Critical Darlings.

In addition to this, he worked on the writing and recording of two songs on mathcore band The Dillinger Escape Plan's 2010 release, Option Paralysis.

In this year he also collaborated with Melissa Auf der Maur on her second album Out of Our Minds, playing piano in two songs "The Hunt" and "Father's Grave".

[10] Garson premiered a new commissioned work in 2014, written in collaboration with medical patients in partnership with brain surgeon Dr. Christopher Duma of the Foundation for Neuroscience, Stroke and Recovery.

[16] In December 2018, Garson returned to perform with both The Smashing Pumpkins and Nine Inch Nails in separate Los Angeles area concerts.

[17][18] Mike continued his collaboration with Reznor in 2019, composing the opening piano number for his HBO series Watchmen score.

[25] Garson is also featured on the If I Can't Have Love, I Want Power album by Halsey on its bonus track "People Disappear Here".