He spent his childhood and adolescence in Barcelona, where he studied architecture. In 1980 he founded the label Custo Line with his brother David which in 1996 became Custo Barcelona and today is a label of Blue Tower S.L., Barcelona. Initially focusing on printed tops and T-shirts inspired by the looks of Californian surfers, the label meanwhile has added a full range of women's clothing, a men's line, as well as shoes and accessories. Since 2008 licenses for fragrances and perfumes have been issued.
Custo Dalmau is married to Eva Vollmer who is responsible for the label's kids line Custo Growing. Custo Dalmau is father to 2 daughters (one of which is not his biological daughter) and two sons. He spends his time between the family home in Barcelona and the USA which is the most important market for Custo Barcelona.