Metropolitan Police confirmed they had arrested the man in Manchester, north west England, "on suspicion of harassment offences."
Caroline Criado-Perez was bombarded with abusive messages after successfully lobbying for the "Pride and Prejudice" author to replace Charles Darwin on Britain's £10 notes from 2017.
She said the abusive tweets began to appear on Wednesday, the day the Bank of England (BoE) announced its decision.
Police said officers in Camden, London, received an allegation of "malicious communications" after Criado-Perez reported she had received "about 50 abusive tweets an hour for about 12 hours".
She added that she had "stumbled into a nest of men who coordinate attacks on women".
The opposition Labour Party accused Twitter of an "inadequate response" to the abuse and an online petition was set up calling for the web giant to introduce a "report abuse" button.
"Of course it is right to report such abuse to the police," shadow home secretary Yvette Cooper wrote in a letter to Twitter.
"But social media platforms also have a responsibility for the platform they give users."
Campaigners on Wednesday hailed the BoE's decision as "a brilliant day for women and a fantastic one for people power" after 35,000 people signed an online petition to put a woman on the new note.
The Bank of England announced in April that the image of wartime prime minister Winston Churchill would be put on the £5 note from 2016, replacing the face of 19th century social reformer Elizabeth Fry.
This would have left Queen Elizabeth II, whose face is on every British coin and banknote, as the only woman.
Austen is only the third female historical figure to win a place on a banknote since the policy was introduced in 1970.
The Bank of England said on Wednesday that it had never been its intention to leave British banknotes without a single woman on them.