Mechanisms are organized collections of objects and activities that underlie certain phenomena/behaviours. In this article, I shall argue that the organizations of mechanisms should be thought of as external relations, namely, as relations that do not entirely depend on their relata’s existence, nor on their natures, nor on their intrinsic properties. After having introduced in the first two sections mechanisms and the ontology of relations, I shall analyse the organizations of mechanisms along four different dimensions: spatial, temporal, causal and hierarchical. (...) I shall demonstrate that each dimension requires that organizations be taken as external relations. Finally, in the last section, I shall anticipate and reply to two objections. (shrink)