Nepenthes dubia was first collected on May 29, 1917 by H. A. B. Bünnemeijer on Mount Talakmau, at an altitude of around 1900 m above sea level. Eleven years later, B. H. Danser formally described N. dubia in his seminal monograph The Nepenthaceae of the Netherlands Indies. Danser noted similarities between N. dubia and the closely related N. inermis and suggested that it might represent a natural hybrid involving this species. He wrote: