Career
Johnson started out playing for Nimba FC in his homeland Liberia before traveling to Norway in 2011 to trial with FK Haugesund. He impressed the Norwegian club, but only enough for them to offer him a youth contract, so he instead signed with Swedish club Dalkurd FF. He would however only stay there for a couple of months due to work permit problems. Johnson remained in Sweden though and played for fourth tier club Assyriska IF KF during the second half of the 2011 season.
For the first half of the following season Johnson stepped down one division and played for fifth tier club Juventus IF before once again returning to the fourth tier when playing for Härnösands FF during the fall. After the season he was awarded the title of "best midfielder" in the league Härnösand played in. Before the 2013 season Johnson trialed with second tier Superettan club Jönköpings Södra IF but was turned down.
Instead he signed a three-year deal with third tier club IK Frej. In his second season with them Johnson, who was now playing as forward, became their top goalscorer as the club was promoted to Superettan. In December 2014 Allsvenskan club Djurgårdens IF announced that they had signed Johnson on a four-year deal.
Sam Johnson made his Allsvenskan debut for Djurgården in the 1–2 loss against Elfsborg on 5 April 2015. He made his first Allsvenskan goal in the 1–2 loss against Hammarby on 13 April. Johnson played with the Liberia U23 National Team in 2011 for which he scored six goals in eight games.
In 2015 he started playing for the Liberia national football team.
