Invasive species is an important cause for loss of biodiversity and degradation of ecosystems. However, researches on invasive species often ignore the belowground invasive species, for example, the earthworms. In recent years, an invasive earthworm, Pontoscolex corethrurus, originated from South America has been found and widely distributed in Taiwan. This paper reviews studies on the impacts of P. corethrurus on forest ecosystems, including those on soil physics, nutrient cycling, and soil biota. We suggest the potential impacts of this invasive earthworm on Taiwan’s forest ecosystems should not be ignored and urge for assessments on its distribution and impacts on the ecosystems for future management.