Abstract Trace fossils amongst other sedimentological features are one of the key sedimentological parameters commonly used to assess paleoenvironment. This paper discusses on the occurrence of trace fossil of ichnogenera Ophiomorpha observed in outcrops of Temburong and Belait formations around Klias and Kudat peninsulas. The burrows which are commonly observed at the outcrop sites belong to four ichnospecies: O. rudis, O. annulata, O. recta and O. nodosa. They are variably oriented from vertical to sub-vertical and horizontal, branched to unbranched. In Temburong Formation, O. rudis, O. annulata, O. recta ichnospecies were observed quite commonly which are associated with deep marine environment. Meanwhile, Ophiomorpha nodosa that typically related with shallow-marine trace fossils only observed in Belait Formations. Based on the trace fossil occurrence in conjunction with other sedimentological observations, the paleoenvironment assessment was further improved.