Lower Miocene Nukhul Formation of two onshore wells (ARS-6 and SIDRI-20) situated in the Eastern side Gulf of Suez was investigated for their planktonic foraminiferal content to define its geologic age. The identified planktonic foraminifera contain 20 species belonging to 9 genera. The allocation of the planktonic foraminifera proposes two planktonic biozone of ARS-6 well. The Nukhul Formation is the oldest syn-rift deposits in the Gulf of Suez rift system in Egypt and it is an important exploration target and oil-producing reservoir in the Gulf of Suez. It is the primary hydrocarbon producer for fifteen fields in the region. However, local tectonics affect the reservoir quality and determining the exact age of the Syn-rift Nukhul Formation. This research aims to determine the age of the first Syn-rift rock unit in the Abu Rudeis-Sidri field using planktonic foraminifera. The age of Nukhul Formation is a controverse and previous work on them show the differences in their ages. The biostratigraphic analyses indicate that the Nukhul Formation reveals Burdigalian age.