Raised in an increasingly prosperous family, he was trained in his father's banking business and lived at home until age twenty-nine, when he acquired a modest residence at 33 Neue Mainzer Strasse in Frankfurt in preparation for his marriage on 16 September 1818 to Adelheid Herz (1800–1853).

As a result of Carl's success, the Rothschilds had a substantial banking presence in England and three other major European capitals, giving the family considerable influence and an advantage over their competitors.

During the winter of 1826, Leopold of Saxe-Coburg, future King of the Belgians, was a guest of Carl Freiherr von Rothschild at his villa in Naples.

In 1829, Carl was appointed consul-general of Sicily at Frankfurt and in January 1832 the Jewish banker was given a ribbon and star of the Sacred Military Constantinian Order of Saint George at a ceremony with the new Roman Catholic Pope, Gregory XVI.

In 1841, he bought the Villa Pignatelli at Riviera di Chiaia, with a spectacular view of the Sea and Vesuvio Volcano.