Investment treaty arbitration cases have traditionally seen concerns arising out of the conduct of the investor raised at the merits phase as justification for, or to excuse, actions by host states which may have infringed the investor’s treaty rights. Increasingly, however, in an attempt to have the arbitral tribunal dismiss the investor’s claims without examination of their merits, respondent states are raising, at an early stage of the arbitration, allegations of investor misconduct, as objections to (i) the tribunal’s jurisdiction and/or (ii) the admissibility of the claims. Can such objections prevail and, if so, do they provide evidence of growing recognition of a clean hands doctrine in investment treaty arbitration? This article considers the evidence for arguing that investor-state tribunals can use the clean hands doctrine (and have done so). It looks at the history and use of the clean hands doctrine as a corrective effect and analyses the extent to which the doctrine is recognised in international investment law, looking at both arbitral case law and the legal arguments in favour of its use. Finally, this article discusses the legal effect of the clean hands doctrine and whether the doctrine should operate as an objection to the tribunal’s jurisdiction or as a ground for inadmissibility of the claimant’s claims.