AbstractThe flux of eruptible magma into a magmatic plumbing system influences eruption size and timing. If magma transfer is possible between two hydraulically‐connected magma lenses, system destabilization can tap a larger magma volume than stored in any one melt lens. This study identifies two distinct magma reservoirs beneath Ambrym, a basaltic island volcano in Vanuatu, during the time period February 2019 to January 2022. Using InSAR time series and a data assimilation approach, we estimate pressure changes within two reservoirs (located 5–7 and 4–6 km b.s.l.). Furthermore, a theoretical model demonstrates that the reservoirs may not currently be hydraulically connected, despite evidence of physical mixing of magma derived from each reservoir during the December 2018 eruption. These findings further our understanding of how magmatic plumbing systems at basaltic calderas may change after rift‐zone eruptions.