Born in Caboolture, Queensland, he is the son of Australian Test cricketer Craig McDermott and brother of Alister McDermott. The McDermott family moved to the Gold Coast when Ben was seven years of age and the two siblings began playing junior cricket for Runaway Bay and Broadbeach. Ben made his first XI debut for The Southport School in year 9 and made a remarkable double-hundred for the Gold Coast Dolphins at under-17 level. He also represented Australia in Youth One Day Internationals at Under-19 level.

McDermott made his Big Bash League debut in the 2013-14 season for Brisbane Heat, scoring 30 in his first match against Adelaide Strikers. He had signed a rookie contract at the start of that season but didn’t make his debut for the Bulls until the following summer where he made scores of 0 and 2. In 2015 McDermott signed a rookie deal with Tasmania. After a few years of hovering on the fringes of domestic cricket, McDermott blasted into the spotlight in the 2016-17 BBL when he smashed 114 off 52 balls for the Hobart Hurricanes against the Melbourne Renegades. In the 2018-19 JLT One Day Cup, McDermott was named Player of the Tournament after scoring 427 runs at an average of 71.16 with 2 100s and 2 50s. This lead to him being named in Australia’s Twenty20 International (T20I) squad for the series against Pakistan in October 2018 and he made his T20I debut for Australia in the one-off match against the United Arab Emirates on 22 October 2018. In November 2018, he was added to Australia’s One Day International (ODI) squad for their series against South Africa, but he did not play.