The birth of South Sudan falls directly in the demarcation zone of the rivalry between downstream and upstream riparian states on the waters of the Nile River. The downstream states—Egypt and Sudan—stress their “natural and historic” rights to the entire flow of the Nile based on the 1959 Nile Agreement and older colonial treaties, while the upstream African states refuse to be bound by colonial treaties and claim their equitable share of the Nile River by promoting South Sudan’s accession to the Cooperative Framework Agreement (CFA). The Nile River Basin lacks an international binding water agreement that includes and satisfies all the riparian states. This Article analyzes the status quo of South Sudan’s water rights to the Nile River by addressing the following questions: Is the new state bound by any rights and obligations established by the 1959 Nile Agreement? Is it advantageous for South Sudan to accede to the CFA, which provides for modern principles of international water law? The Article applies the customary international law of state succession to South Sudan’s secession from Sudan to determine if the 1959 Nile Agreement is binding between the two states. It concludes that South Sudan succeeded Sudan with regard to territorial rights and obligations established by the 1959 Nile Agreement, as customary international law recognizes that legal obligations of a territorial nature remain unaffected by state succession. South Sudan should enter into negotiations on a binding water agreement to allocate the 18.5 billion cubic meters of water granted to it under the 1959 Nile Agreement. The Article concludes that South Sudan should accede to the CFA within its allotted portion of the Nile waters under the 1959 Nile Agreement.