Maccarone returned to Middlesbrough for the 2005–06 season, and despite not being a regular first-team player, endeared himself to the Middlesbrough fans, especially through his work-rate and attitude. The player's spell at Middlesbrough is remembered for two last minute winners in key UEFA Cup ties in 2006. He scored against Basel in the second leg of the quarter-finals, a tie in which Middlesbrough overturned a three-goal deficit to win 4–3 on aggregate. In the semi-final of the same competition he came on as a substitute and scored twice in the aggregate 4–3 win over Steaua Bucharest, scoring one of Middlesbrough F.C's most iconic goals of all time, once again in the 90th minute, taking "Boro" to the final in Eindhoven, in which he came on as a substitute. Following his exploits in the semi-final, fellow Middlesbrough striker Jimmy Floyd Hasselbaink declared "Massimo, I love him until I die... it's unbelievable".