"Nepenthes bellii" is closely allied to "N. merrilliana" and "N. surigaoensis" and shares with these species a similar morphology of the pitchers and laminae as well as a reddish colouration of the uppermost leaves. It is not easily confused with them, however, because it is much smaller in all respects, particularly in the size of its pitchers and inflorescence. More generally, "N. bellii" appears to fall under B. H. Danser's classical "Insignes" group, which also includes "N. burkei", "N. insignis", "N. merrilliana", and "N. ventricosa", among others, with "N. sibuyanensis", "N. barcelonae" and "N. aenigma" being recent additions.