The Australians toured England in 1905, but MacLaren was again passed over for the England captaincy; the team was captained by Jackson and won the series 2–0. MacLaren began the season well and played in the first Test. Australia led by 25 runs after the first innings, as England struggled to play the pace of Albert Cotter. According to a story later told by Neville Cardus, before the second innings he saw MacLaren muttering: "Cotter! I'll bloody Cotter him!". MacLaren attacked Cotter's bowling, and overcame the defensive bowling tactics used by Australia to slow down the game. He scored 140, his highest Test innings and only Test century in England. When Australia batted, Bernard Bosanquet took eight wickets to bowl England to a win; it was MacLaren's suggestion that Jackson persist with Bosanquet's bowling when it was initially unsuccessful. MacLaren scored 56 and 79 in the drawn second Test, but did not play in the third owing to injury. He played in the final two Tests but accomplished little. In the series, he scored 303 runs at 43.28. Jackson later wrote that MacLaren was an invaluable tactical aid during the series. Lancashire ended the season second in the Championship, and opened a testimonial fund for MacLaren which raised over £800 by the end of the season. He later clashed with committee members who were unhappy with his decision to use the money to buy a motor car. At the end of the season, MacLaren resigned the captaincy of Lancashire, but was persuaded to continue by the committee. In total during 1905, he scored 1,522 runs at an average of 35.39 in all first-class cricket.