Mjällby Allmänna Idrottsförening, usually known by the more simple name of Mjällby AIF, was first established back in April 1939. Based in Hällevik, they are affiliated with the Blekinge Football Association.
The club has spent the vast majority of its history outside of the top flight of Swedish football, only making occasional ventures into the Allsvenskan. Indeed, during the 1950s, 1960s and 1970s, the club occasionally fell as far as the fourth tier. Mjällby first gained promotion to the second tier during the 1970s and then gained promotion again, from the second tier to the top tier, at the conclusion of the 1979 season. Their first Allsvenskan appearance came in 1980, but they were immediately relegated at the end of the campaign. Since that time, the team have primarily competed in the top two divisions, but have struggled to fully establish themselves amongst the country's elite sides, suffering multiple relegations after reaching the Allsvenskan.
To date, major honours have been out of reach for the side, who have instead only tasted success in the lower divisions. In the 1988 season, they were runners up in the Swedish Football Division 1 Södra. More recently, in 2009, they were crowned champions of Sweden's second tier, the Superettan. This minor trophy remains the only notable piece of silverware the club has won so far. In 2010, Mjällby enjoyed their greatest ever domestic league campaign, as they finished the Allsvenskan season in 6th place.
Amongst the best-known players to have played for the club are Swedish internationals like Anders Linderoth and Christian Wilhelmsson. Anders Linderoth's son, Tobias Linderoth, was a product of the side's youth academy.
Mjällby currently play their home matches at Strandvallen, which first opened in 1953. The stadium underwent renovations in 2002 in order to bring it up to modern standards and the ground's capacity was subsequently expanded in both 2010 and 2012. At present, it is able to hold a maximum of 7,000 supporters.