A philanthropist, in 1892 he established the charitable Fresh Air Fund, still in operation and now known as Pearson's Holiday Fund, to enable disadvantaged children to partake in outdoor activities.
In 1897, Pearson married, as his second wife, Ethel Fraser, daughter of William John Fraser. (His first wife was the daughter of Rev John Bennet.)
In 1898, he purchased the Morning Herald, and in 1900 merged it into his new creation, the halfpenny Daily Express. The Express was a departure from the papers of its time and created an immediate impact by carrying news instead of only advertisements on its front page. He was also successful in establishing papers in provincial locations such as the Birmingham Daily Gazette. He came into direct competition with the Daily Mail and in the resulting commercial fight almost took control of The Times, being nominated as its manager, but the deal fell through.
In 1900 Pearson despatched the explorer Hesketh Prichard to Patagonia to investigate dramatic reports of a giant hairy mammal inhabiting the forests, and conjectured to be a giant ground sloth, long since extinct. Prichard's reports from 5,000 miles away gripped readers of The Express, despite him finding no trace of the creature.
During this same period, Pearson was also active as a writer, and wrote a number of tourist guides to locations in Britain and Europe. Under the pseudonym of "Professor P R S Foli", he wrote Handwriting as an Index to Character in 1902, as well as works on fortune-telling and dream interpretation.
In 1904 he purchased the struggling The Standard and its sister paper the Evening Standard for £700,000 from the Johnstone family. He merged the Evening Standard with his St James Gazette and changed the Conservative stance of both papers into a pro-Liberal one, but was unsuccessful in arresting the slide in sales and in 1910 sold them to the MP Sir Davison Dalziel and Sir Alexander Henderson.
Later completely blind, Pearson was made president of the National Institution for the Blind in 1913, raising its income from £8,000 to £360,000 in only eight years. In 1915, he founded St Dunstan's Home for soldiers blinded by gas attack or trauma during the First World War. Its goal, radical for the times, was to provide vocational training rather than charity for invalided servicemen, and thus to enable them to carry out independent and productive lives.
Pearson was a close friend of the pioneer of the Scouting movement Baden-Powell, and supportive of his efforts in setting up the movement and publishing its magazine The Scout. When Pearson's scheme for publishing in Braille was faltering due to lack of funds, on 2 May 1914 Baden-Powell publicly requested that "all Scouts perform a 'good turn' for The Scout magazine publisher Mr C Arthur Pearson, in order to raise money for his scheme of publishing literature in Braille for the blind."
In 1919, Pearson wrote the book Victory over blindness: how it was won by the men of St. Dunstan's.
He founded the Greater London Fund for the Blind in 1921.