An important aspect of solar activity is the coupling between eruptions and the surrounding coronal magnetic field topology. This coupling determines the trajectory and morphology of the event and can even trigger sympathetic eruptions from multiple sources. Here we report on a numerical simulation of a new type of coupled eruption, in which a large-scale coronal jet initiated by a pseudostreamer filament eruption triggers a streamer-blowout coronal mass ejection (CME). The initial pseudostreamer in our simulation is typical of many observed pseudostreamers in that it separates an equatorial and polar coronal hole and is associated with a broad S-Web arc in the heliosphere. Our results show that the coupled eruption is a result of the enhanced breakout reconnection that occurs above the erupting filament channel as the jet is launched and progresses into the neighbouring helmet streamer. This partially launches the jet along closed helmet streamer field lines which blows out the streamer top to produce a classic bubble-shaped CME. Another key finding is that the CME is strongly deflected from the jet’s initial trajectory and contains a mixture of open and closed magnetic field lines. We present the detailed dynamics of this new type of coupled eruption and discuss the implications of this work for interpreting in-situ and remote-sensing observations and for understanding CME formation and evolution in general.