The son of Emich Eduard Karl V Fürst zu Leiningen and Feodore Viktoria Alberta Prinzessin zu Hohenlohe-Langenburg, Prinz Hermann Viktor Maximilian zu Leiningen was from Amorbach in Germany. He started racing in 1927, mainly competing with in hillclimbs.
Between 1928 and 1929 occasionally drove an Amilcar and Mercedes SSK .
Between 1930 and 1932, he was part of Burggaller's German Bugatti Team along with H.J. von Morgen. von Morgen and Hermann then won the Masarikuv Okruh (Czechoslovakian Grand Prix) in a Bugatti T35B in 1930. This was the inaugural event at the brand new Masaryk-Ring. At the start Caracciola's Mercedes-Benz took the lead with Von Morgen's Bugatti in hot pursuit. Caracciola then lost his engine and when von Morgen develpoed difficulties in his leading Bugatti, Morgen he swapped cars with zu Leiningen. As a result, Morgen lost a full lap. Leiningen, in Morgen's car, keeped the lead for a while until the ailing Bugatti came to a grinding halt. Nuvolari then took the lead but von Morgen re-took the lead five miles from the finish when Nuvolari's Alfa Romeo overheated.
Driving his Bugatti T35C in 1931, he retired from the Monaco Grand Prix after 31 laps with gearbox problems. He also retired from the Eifelrennen and the AVUS Rennen but finished the season with a fifth in the Czechoslovakian Grand Prix at Brno.
He effectively retired at the end of 1931 but was called up by Auto Union in 1934 to be part of the works team. So on May 27, 1934, when Auto Union raced for the first time on the Avus circuit in Berlin, their drivers were zu Leiningen, Hans Stuck and August Momberger. Momberger finished third after the other two had retired.
The team retained the services of Hans Stuck and Hermann zu Leiningen and added Achille Varzi to their line up for 1935. In May at the fifth Avusrennen, freightened by his experience in Tunis GP when the car had caught fire without him noticing in the enclosed cockpit, Stuck elected to drive an open racer (B-type chassis 760012). Varzi also raced one of the new cars while zu Leiningen and Rosemeyer, who was making his debut on four wheels, had to be content with streamlined A-type cars. He retired with engine problems in the second heat. In June he went to the Eifel GP as a reserve driver. In the race Varzi, who had started the race in pain from an appendicitis, could not continue and handled over the car to zu Leiningen who came home in 9th place. He was a reserve a gain at the French Grand Prix but his serviecs were not required.
He did make one start that year with the ERA-B for the works team at the Prix de Bern in Bremgarten, Switzerland.
In February 1936 Auto Union announced that Varzi, Stuck and Prince zu Leiningen would form the 1936 team, but by the time the season started Rosemeyer's name had replaced that of zu Leiningen who happily went back into retirement.
He married Irina Gräfin von Schonborn-Wiesentheid on 21 December 1938.
In the early 1950s he entered a few rallies.