The 23-year-old attended the event alongside his model girlfriend Isobel Richmond, 20, who complemented him in a quirky Dolphin-print top.
The young couple went public with their relationship last October and have been regularly pictured together at fashion events since.
Previously, Richmond, a fashion communication and business student at the University of Brighton, told The Standard that she and Gallagher met at a gig.
She said: “We met at a gig at a small bar called The George Tavern [in Stepney] around nine months ago.
“Brighton’s a fun place, but you can’t keep me away from London for more than a couple of days. I’m just having the best time seeing what London has to offer.”
Lennon is Gallagher and Kensit’s only son from their three-year marriage. He was born a year before their split in 2000.
Givenchy #GENTLEMANSOCIETY Fragrance Launch at The Vinyl Factory
While actress Kensit has an older son, James, with ex husband, Scottish singer Jim Kerr, 63.
Aside from the budding model, the star-studded fragrance launch for Gentleman Society was also attended by Jim Chapman, Elfie Reigate, Lola Bute, and Oliver Proudlock as well as face of the campaign composer, Benjamin Clementine.
Guests at the immersive event were treated to an intimate live performance by Grace Carter, while Mary Charteris, Kim Turnbull and Hale Zero provided DJ sets.