Upon graduation from the Imperial and Royal Naval Academy in Fiume (now Rijeka), he joined the fleet in Pola (Pula) in 1877 as a Seekadett.

[3][4] At the outbreak of the First World War in 1914 he was named commander of the 1st Division of the 1st Battle Squadron, hoisting his flag in the dreadnought battleship Tegetthoff.

Promoted to full Admiral, he was appointed to the additional post of Chef der Marinesektion in April 1917, succeeding the late Karl Kailer von Kaltenfels.

[6] Relieved of command, Njegovan was succeeded as Flottenkommandant by Miklós Horthy and as Chef der Marinesektion by Franz von Holub.

Pensioned and promoted to Grossadmiral on the retired list, he was decorated with the Grand Cross of the Order of Leopold for his services to the Empire.

His homeland of Croatia had become part of the new country of the Kingdom of Serbs, Croats, and Slovenes, and in 1930 he died in his hometown of Zagreb at the age of 71.