Karl Merizzi was born as the son of a k.k. Rittmeister at Como on the 26th of October 1839. On the 25th of September 1851 he entered military services by attending the military academy at Wiener Neustadt. On the 1st of June 1859 he was commissioned as a Leutnant in infantry regiment number 22. With this regiment he took part in the campaign in northern Italy of the same year. During the battle near Palestro, Merizzi received a serious bullet wound to the chest and was captured by the enemy. After his release he was transferred to infantry regiment number 79 on the 31st of January 1860 and send on convalescent leave to recover from his wounds.
On the 28th of July 1864 Karl Merizzi entered service in the Mexican Volunteer Corps in the rank of Oberlieutenant. He took part in the expedition to the Sierra del Norte, the Sierra Madre and through the Tierra Caliente. He was promoted to Hauptmann 2nd class on the 11th of November 1865. For his heroic performance he was honored with the Knight's Cross of the Order of our beloved Madonna of Guadalupe on the 2nd of January 1866 and the Bronze Military Merit Medal on the 31st of January 1866 with the additional promotion to Hauptmann 1st class. When the volunteer corps were disbanded in December 1866 he returned to Austria were he was re-transferred into the Austro-Hungarian army as Leutnant in infantry regiment number 79 on the 7th of April 1867. Like so many others, who were lucky enough to survive the Mexican Adventure, he found himself in his old regiment with the same rank he had had in 1864 feeling the mockery and sometimes scorn of his comrades who had remained at home. During these years the spirit of the time was that the "Mexicans" were often seen as traitors having a good time in a tropical climate while the Austrian Kaiser had needed them during the fateful war of 1866. Some circles in the Austro-Hungarian Monarchy who in the defeat following the Austro-Prussian war thought that they had lost everything and took out their resentment on the veterans of the Mexican Adventure. It took years to overcome these resentments.
Karl Merizzi was promoted to Oberleutnant on the 23rd of April 1869. On the 7th of January 1872 he married Anna Lesnig with whom he had a son called Erik (in some sources Erich) who later also entered on a military career. On the 1st of October 1873 Oberleutnant Merizzi was transferred to infantry regiment number 7 but only a month later on the 1st of November he was again transferred, this time to infantry regiment number 17 garrisoned at Trieste and Laibach. In this regiment he received his promotion to Hauptmann 2nd class on the 1st of November 1877 and to Hauptmann 1st class on the 1st of November 1880. On the 1st of May 1889 Hauptmann Merizzi was transferred to infantry regiment number 62 with the additional promotion to Major shortly followed by his retirement on the 1st of December 1889. Because of the regulations of the time his service in the Mexican Volunteer Corps was taken into account as "wartime duty" and Major Merizzi was ennobled as "Edler von" on the 9th of September 1890 as a common policy . In September 1891 Major Karl Edler von Merizzi and his wife Anna moved to Vienna where he died on the 20th of December 1914.