It was named by Louis L. Jacobs and colleague, Maeve Mercredi Fourie and was originally described in 1928 by Sidney H. Haughton as a species of Gigantosaurus (an invalid name for the diplodocid currently known as Tornieria). Haughton considered it closely related to the species G.robustus (later the type species of Janenschia). They are currently recognised as separate but related forms of titanosaur.
Relatively small by sauropod standards, Malawisaurus reached lengths of around 16 metres (52 ft). Like some other titanosaurs, ossicles have been found which are believed to represent dermal scutes that covered the skin.
The vertebrae from the middle part of its tail had elongated centra. Malawisaurus had vertebral lateral fossae that resembled shallow depressions. Fossae that similarly resemble shallow depressions are known from Saltasaurus, Alamosaurus, Aeolosaurus, and Gondwanatitan. Venenosaurus also had depression-like fossae, but its "depressions" penetrated deeper into the vertebrae, were divided into two chambers, and extend farther into the vertebral columns.