Abstract: The investigative power of arbitrators is a complex creature. On the one hand, it bears the marks of the contractual basis of arbitration. On the other, it shows signs of the quasi-judicial role of arbitrators. A fruitful way to tackle this topic consists in addressing the sources of such power, as well as the fine line separating law and facts. The analysis will point out the importance of keeping a balanced approach to parties' expectations, both in the exercise of the investigative power and in the separation of law and facts.