Adelaide was the daughter of Manfred del Vasto
Her paternal grandparents were Teto II del Vasto, and his wife Berta, daughter of margrave Odalrico of Turin.
She married as his third wife Roger I of Sicily in 1089.
Roger I died in 1101, and Adelaide ruled as regent of Sicily for her young sons Simon and Roger II. During her tenure, the emir Christodulus rose to preeminence at the court and Palermo was settled as the capital of the realm.
Around 1112 she married Baldwin of Jerusalem. She brought to this marrige an enormous amount of badly needed money, as well as some Muslim archers and a thousand other Sicilian soldiers.
This marriage was annuled in 1177 at Acre, because it was considered a bigamous marriage since Baldwin's wife Arda was still alive.
After the annulment Adelaide sailed back to Sicily.
She died on April 16, 1118 and was buried in Patti. Roger II was outraged at the treatment of his mother and never forgave the Kingdom of Jerusalem. Almost thirty years later, Roger still refused to give assistance to the Crusader states during the Second Crusade.