Achilleas Diamantis was born in Athens. He started playing electric guitar at the age of 10 and after a few years he started performing with local rock bands. In 1989 he graduated from "Papantonopoulou Sound Engineering School". He continued studying abroad and in 1992 he graduated from the Guitar Institute of Technology (GIT) of the Musicians Institute (MI) Hollywood California.There, he attended courses with top class famous musicians, such as Scott Henderson, Frank Gambale, Don Mock and Joe Diorio.

He returned to Greece and started his music career as session guitar player, collaborating with many pop stars. He has participated in more than 100 album recordings and has made hundreds of personal appearances in concerts and TV shows in Greece and also abroad.

Achilleas Diamantis formed his first jazz-fusion band Confusion and released the homonymous album in 1999. In 2005 he started teaching modern guitar in "Art Music School" of Yiorgos Fakanas.