He was the son of Nathan Mayer Rothschild, 1st Baron Rothschild and Emma Rothschild (née von Rothschild).
Charles predeceased his older brother Walter Rothschild, 2nd Baron Rothschild (1868-1937) who died without issue (that is to say, without children). The peerage therefore passed to Charles's son Nathaniel Mayer Victor Rothschild, 3rd Baron Rothschild.
He attended Harrow, an experience he found traumatizing for incidents of anti-Semitism. "If I ever have a son," he wrote to his wife, "he will be instructed in boxing and Jiu-Jitsu before he enters school, as Jew hunts such as I experienced are a very one-sided amusement and there is apt to be a lack of sympathy between the hunters and the hunted".
Charles Rothschild worked as a partner in the family bank NM Rothschild and Sons in London. However, like his zoologist brother, he devoted much of his energies to entomology and natural history collecting. His collection of fleas is now in the Rothschild Collection at the British Museum. He also discovered and named the plague vector flea, Xenopsylla cheopis (Rothschild), also known as the oriental rat flea, at Shendi, Sudan, on an expedition in 1901, publishing his finding in 1903.
Charles went to Rothschild's Bank every morning; despite all his interest in science and in natural history, he never missed a day. He was also very interested in the gold refinery operated by Rothschilds and invented all sorts of things for collecting gold, and working on gold from a scientific point of view.
Today Charles Rothschild is regarded as a pioneer of nature conservation in Britain. During his lifetime he built and managed his estate at Ashton Wold in Northamptonshire to maximise its suitability for wildlife, especially butterflies. He was concerned about the loss of wildlife habitats, and in 1912 set up the Society for the Promotion of Nature Reserves, the forerunner of The Wildlife Trusts partnership. In 1915 the Society produced a schedule of the best wildlife sites in the country, some of which were purchased as nature reserves.
In 1907 Charles Rothschild married Rozsika Edle von Wertheimstein (1870 – 30 June 1940), a descendent of the first openly Jewish family in Europe to be ennobled. She was born in 1870 at Nagyvarad, Hungary (now the Romanian city of Oradea), the daughter of a retired army officer, Captain Alfred Edler von Wertheimstein.
Rozsika was one of seven children. She was a very beautiful woman with dark brown eyes. Each eye had a purple ring to it, and they could flicker strangely. She was a voracious reader. Every day she had a Hungarian newspaper, a German newspaper, an English newspaper, and quite often a French one, too, and she read all the political articles in these papers. Rozsika had been a champion lawn tennis player in Hungary.
After their marriage on 6 February 1907, they lived at Tring and in London. Charles, who worked in the family’s banking business was a dedicated naturalist in his spare time: the young couple had met on a butterfly-collecting trip in the Carpathian Mountains. In the evening, the Rothschilds might go together to a concert or a dinner party, but Charles really preferred to sort out his butterflies. Charles's tragic suicide in 1923 when he was 46 years old was a terrible shock to his wife and four children. Rozsika von Wertheimstein died on 30 June 1940.
They had four children: