The town has traditionally lived of fishing. The nearby harbour of Nogersund is the third largest fishery harbour in Sweden. The fishery industry is also dominant on the peninsula. Listerlandet is also the fur farming centre of Sweden. Fur farming is currently under heavy political debate in Sweden.
Mjällby is known for its football team which has played in the Swedish national football league a few times. Among soccer fans in Sweden the team of Mjällby AIF is known as "the team that always returns". In 2007 they played in the "Superettan", the second highest division.
The mathematician Lars Hörmander was born in Mjällby.