A right-hand bat and right-arm fast-medium pace bowler, Mason played county cricket for Kent between 1893 and 1919. With a height over six feet, and an attractive, elegantly straight play with the bat, Mason was considered "one of the finest amateur allrounders to play for Kent". A prolific all-rounder, Mason excelled as a schoolboy cricketer for Winchester College, scoring 147 and 71 along with eight wickets in one match against Eton in 1892.
He was described by Wisden in 1898, the year he was named Cricketer of the Year, as "beyond all question the finest batsman turned out in our time by Winchester College." He left the school with a batting average of over 48, and a bowling average of only 18.
He went on to play as an amateur for Kent in 1893, and despite a lacklustre second season became a stalwart performer. He assumed the captaincy in 1898 from incumbent Frank Marchant, a position he held for five seasons until his career as a solicitor took precedence.
He scored 1,662 runs at 53, and took 78 wickets at 19 in 1900, following that with 1,467 runs at 92 wickets in 1901. In all he scored 13,363 runs and took 675 wickets at 21.
His highest score of 183 came against Somerset at Blackheath while he posted an unbeaten 181 against Nottinghamshire at Trent Bridge.
He scored three successive centuries in 1904 against Yorkshire, Somerset and Essex.