The conflicting objectives of the Energy Charter Treaty’s (ECT) protection of fossil fuel investments and climate change mitigation can reveal themselves in investor state dispute settlement (ISDS). As neither the modernization nor the termination of the ECT is likely, ECT arbitration will continue to exist. This article, therefore, examines the reconciling potential of integrative interpretation in climate relevant ECT arbitrations. An integrative interpretation is not only prescribed by the international rules of treaty interpretation, but can also be found in the practice of international dispute settlement. However, international climate law has not yet been taken into account by a single ECT tribunal. Although some hurdles and uncertainties remain in practice, examples of extraneous treaty use, as well as the reasoning of the judgments of recent climate litigation, show that ECT ISDS has the potential to reconcile climate change and energy investment interests in the future.