Ahmed began his musical career at a young age, when he grew up in a musical family. His father, Kamal Das Gupta, was a noted music director, while his mother, Feroza Begum, was a Nazrul Sangeet singer. Shafin took lessons about Nazrul Sangeet in his childhood. He was exposed to western musical influences since he studied in England, along with his elder brother, Hamin Ahmed. They then founded Band Miles which went on to become a leading musical group in Bangladesh. Shafin produced several songs including Chand Tara Shurjo, Firiye Dao, Jala Jala, Prothom Premer Moto and Fera Alena. His first song, It's Magic (Ki Jadu) was written during his school years.
On January 12, 2010, Shafin left Miles citing personal differences with the band. He formed a new band group – Rhythm of Life. The others members who joined were – Wasiun (Guitar), Shahin (Guitar), Sumon (Keyboard), Shams (Bass Guitar), Ujjal (Percussion), and Rumi (Drums). But Shafin disbanded the new group and returned to Miles at the end of the year.
Shafin is the youngest of three brothers. He has three children – a son, Azraf Rakin Ahmed and a daughter, Raniah Safa Ahmed. They both were born to his ex-wife, Rumana Dowla.