This chapter analyses how investment agreements that purport to include intellectual property (IP) in their scope should be interpreted. The internationally agreed rules of treaty interpretation found in the Vienna Convention require that the object and purpose of a treaty inform its interpretation. When IP is part of an investment treaty then both the object and purpose of investment and of the relevant IP at issue should be part of the interpretative exercise. The chapter examines how the mingling of IP and investment ought to impact the interpretation of object and purpose in light of the scope of intellectual property, intellectual property related investment obligations and the complexities of the relevant international regimes. With reference to recent high-profile disputes, it proposes how the Vienna Convention rules of interpretation can be used effectively to recognise, in consistent ways, the object and purpose of international intellectual property law in its different contexts.