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Graptolites from the latest Ordovician to the earliest Silurian rocks of northwest Peninsular Malaysia are described and reviewed. The fossils were collected previously by C. R. Jones and presently by the authors inside the black mudstones from the basal section of Tanjung Dendang Formation in Pulau Langgun, Langkawi, which comprises assemblages from the Hirnantian Metabolograptus extraordinarius Biozone to the Rhuddanian Akidograptus ascensus–Parakidograptus acuminatus Biozone. The latest Ordovician strata also include a Hirnantia fauna bed between the Metabolograptus extraordinarius and Metabolograptus persculptus biozones, in which shelly fossils such as Mucronaspis sp. could be recovered. A revised graptolite biozonation is proposed for the latest Ordovician to the earliest Silurian succession of northwest Peninsular Malaysia. This interval is significant for understanding the extent of mass extinction events happening right at the end of the Ordovician period and subsequent faunal change in the region.

Graptolites from the Lituigraptus convolutus and Stimulograptus sedgwickii biozones from the topmost 270 cm of the Tanjung Dendang Formation (formerly Lower Detrital Member of the Setul Formation) previously collected by C. R. Jones in Pulau Langgun, Langkawi were reviewed, and revision on the taxanomic were made where necessary. Identified species include: Campograptus lobiferus (M’Coy), Demirastrites sp., ‘Monograptus’ delicatulus Elles and Wood, Normalograptus scalaris (Hisinger), Pseudoretiolites perlatus (Nicholson), Stimulograptus distans (Portlock), Stimulograptus sedgwickii (Portlock), Torquigraptus? decipiens (Törnquist), Torquigraptus cf. denticulatus (Törnquist), Glyptograptus sp. 1? and Glyptograptus sp. 2?. Biostratigraphical link between the graptolite assemblages in Langkawi and the assemblages in British, China and Myanmar is discussed. The revised graptolite assemblages suggest only the Stimulograptus sedgwickii Biozone is present for the topmost 270 cm interval of the Tanjung Dendang Formation.