At 180 cm (5 ft 11 in) tall and 82 kg (181 lb), he plays as a running half-back who can move up forward.

As of the end of season 2024, he has polled a total of 25 Brownlow Medal votes in his career.

[1] Johannisen was born in Johannesburg, South Africa, to mother Sonya from Zambia and father Eldrid from Durban.

Johanissen was recruited by the Western Bulldogs in the 2011 Rookie Draft, with pick #39, and made his debut in Round 19 of the 2012 AFL season against North Melbourne at Docklands Stadium.

Johanissen was adjudged best afield in the Western Bulldogs' Grand Final victory over the Sydney Swans in 2016; he recorded 25 kicks among 33 disposals and 7 marks to win the Norm Smith Medal.