As the world becomes more interdependent and computing grows more collaborative, there is a need for new abstractions and tools to help users work together. We recently introduced entangled queries – a mechanism for information exchange between database queries [6]. In this paper, we introduce entangled transactions, units of work similar to traditional transactions that however do not run in isolation, but communicate with each other via entangled queries. Supporting entangled transactions brings about many new challenges, from an abstract model to an investigation of the unique systems issues that arise during their implementation. We first introduce a novel semantic model for entangled transactions that comes with analogues of the classical ACID properties. We then discuss execution models for entangled transactions and select a concrete design motivated by application scenarios. With a prototype system that implements this design, we show experimental results that demonstrate the viability of entangled transactions in real-world application settings.