As a captain in 1859, he was part of the Austrian forces opposing the Second Italian War of Independence and participated in an action on hotly contested heights of San Martino in front of Solferino.

In 1895 he persuaded Franz Joseph to agree to the religious and political reforms of the Sándor Wekerle ministry.

In 1903 he resigned, together with the prime minister, Kálmán Széll, owing to the rejection of a bill to increase the contingent of recruits, and was appointed captain of the Hungarian Life-Guards organized at that time.

Fejérváry nevertheless succeeded in settling these differences by the so-called Pactum, on the basis of which the Wekerle ministry was formed 8 April 1906.

On the death of Prince Esterházy, Captain of the Hungarian Royal Guard, Fejerváry was appointed his successor.