Career
Breiðablik He had spells with the youth team at Chelsea and Fulham, while studying at the International School of London. After failing to adapt to life in London, he decided to move back to Iceland in 2008, joining his boyhood club Breiðablik as he admitted missing playing football and attending school with his friends. After returning to Breiðablik he quickly established himself as first team regular in the 2008 Icelandic Premier League season.
On 30 September 2008, Bundesliga side Hamburger SV had an offer accepted for Jóhann, the deal did however not go through.
On 28 November 2008, it was reported that Jóhann was on trial at English Championship side Coventry City. Arizona Alkmaar On 28 January 2009 Breiðablik announced that a transfer fee had been agreed with Dutch club Arizona Alkmaar.
Jóhann subsequently signed a 5-year contract with Arizona Alkmaar. Charlton Athletic On 11 July 2014, Jóhann signed for Charlton Athletic on a two-year deal.
Gudmundsson was voted runner-up in the club"s player of the season competition after an impressive first campaign, which saw him Netto a total of 11 goals in 37 matches.
He developed an eye for the spectacular after a host of impressive goals, most notably of which came against Cardiff on Boxing Day. On 22 July 2015, Gudmundsson signed a new four-year deal with the club International goals Scores and results list Icelands goal tally first.