In the face of the Norman conquests, Sergius reinforced the Neapolitan relationship with the Byzantine Empire and was at some point granted the Byzantine title of "protosebastos". He apparently gave aid to the Norman prince Jordan I of Capua when the latter broke his alliance with Pope Gregory VII and did homage for his principality to the German emperor Henry IV. The pope wrote to Prince Gisulf II of Salerno asking him to persuade Sergius to break off his support for Jordan and Henry.