Fornah graduated for the academy at Nottingham Forest, but struggled to break into the first team and had loan spells at Casa Pia, Plymouth Argyle, Shrewsbury Town and Reading.
In August 2023, Fornah left Forest to join local rivals Derby County in a rare direct transfer between clubs.
[4][5] On 31 January 2020, Fornah moved on loan to Portuguese LigaPro side Casa Pia for the remainder of the season, making five appearances.
[18][19] Fornah made 23 appearances during his first season at Derby, as the club secured automatic promotion to the Championship by finishing runners-up in League One.
[22] In November 2023, Fornah received his first call-up to the Sierra Leone national team for World Cup Qualifiers against Ethiopia and Egypt.