The first mention of a Luca Grimaldi is in a document formalising the alliance between Genoa and Milan against the Emperor Frederick II in 1240.
In 1255, a certain Luca Grimaldi married his daughter Alasina to Pasqualino Usodimare, who promised not to consummate the marriage until she was twelve.
In 1258 he was sent as an ambassador of Genoa to the court of Pope Alexander IV and in 1262 he was elected, along with fellow troubadour Jacme Grils and other citizens, as rector of the city.
In 1269 Luca and his brother Bovarello were charged by Charles of Provence, now King of Naples, with receiving the ambassadors of the "Sultan of Babylonia", actually the Abbasid caliph then in Cairo, Al-Hakim I, in Genoa.
The Ghibellines in Genoa, however, rebelled, and, on 28 October 1271, in a major battle, the Guelphs were defeated and many were captured, including Luca Grimaldi, who was imprisoned for twenty three years.