Abstract The classical quorum-sensing (QS) model is based on the assumption that diffusible signaling molecules accumulate in the culture medium until they reach a critical concentration upon which expression of target genes is triggered. Here we demonstrate that the hydrophobic signal N-hexadecanoyl-L-homoserine lactone, which is produced by Paracoccus sp., is released from cells by the aid of membrane vesicles (MVs). Packed into MVs, the signal is not only solubilized in an aqueous environment but is also delivered with varying propensities to different bacteria. We propose a novel MV-based mechanism for binary trafficking of hydrophobic signal molecules, which may be particularly relevant for bacteria that live in open aqueous environments.