Otto's regiment participated in the 1807 War against Napoleon Bonaparte, and the officer was awarded with an Order of St. Stanislaus of 3rd degree. During Napoleon's invasion of Russia Otto von Pfeilitzer-Franck participated at the Battle of Borodino for which he was awarded with an Order of St. Vladimir of 4th degree, also at the Battle of Brienne and Battle of La Rothiere for which he received an Order of St. Anna of 2nd degree. September 4, 1815 he was promoted to the rank of staff-captain (of cavalry) (штабс-ротмистр) of a corps stationed in France and aide-de-camp to Russian general Count Mikhail Semyonovich Vorontsov.