During the 1967–68 series against India, Simpson's all-round performances were exceptional. He scored 55 and 103 in the First Test at Adelaide, then scored 109 and took 4/49 in the Second Test at Melbourne. Australia won both Tests, the second by an innings. After deciding that he would retire at the end of the season, Simpson was omitted for the Third Test so that other players could have international experience before the 1968 tour of England. Simpson returned to the team for the Fourth Test at Sydney in front of his home crowd. In his international farewell, he played under the captaincy of Lawry. Simpson recorded his best Test match figures of 3/39 and 5/99, and claimed five catches in another Australian victory. His final series yielded 294 runs (at 58.80 average), 13 wickets at 16.38 and seven catches.