Volcanic activity on Tenerife Island is extremely diverse. Three radial rift zones are characterized by cinder cones from basaltic fissure eruptions. A triple junction in central Tenerife exhibits a complex of merged, predominantly phonolitic, stratovolcanoes. The Las Caadas caldera and widespread ignimbrite deposits reveal high explosive potential. We investigated the crustal and upper mantle structure beneath Tenerife using local earthquake data recorded by two dense seismic networks on the island. For our tomographic inversion, we selected > 130,000 P and Swave arrivals from 6,300 events that occurred during seismic unrests in 20042005 and 20172021. Synthetic tests confirmed that we could robustly resolve seismic velocity structures to 20 km depth. In the upper crust (down to 7 km) beneath central Tenerife, a prominent highvelocity anomaly represents the rigid core of the volcanic complex; at greater depths, a strong lowvelocity anomaly reveals abrupt crustal thickening. Vp and Vs contour lines of 5.2 and 2.85 km/s, respectively, reveal Moho depth variation; crustal thickness beneath Las Caadas reaches 17 km, whereas that beneath other parts of Tenerife is 10 km. An anomaly at 5 km beneath the caldera with low Vp, low Vs, and high Vp/Vs might be associated with a major phonolitic magma reservoir. Similar anomalies at sea level may represent shallow magma sources responsible for recent eruptions. Seismicity occurs in a columnar area of high Vp, high Vs, and low Vp/Vs, and may represent hydrothermal fluid migration through brittle media. Based on our results, we constructed a conceptual model of volcanic activity on Tenerife. Tenerife is the largest and most populated island of the Canary Islands archipelago. Volcanic activity in Tenerife has the potential to seriously threaten the population and infrastructure. Two main types of volcanism are observed: explosive phonolitic eruptions from the central part of the island and basaltic fissure eruptions along three radial ridges. We present a new seismic tomography model based on the inversion of P and Swave data from local seismicity. Absolute P and Swave velocities reveal abrupt crustal thickening from 10 to 17 km within an elliptical area coinciding with Las Caadas caldera in the central part of Tenerife. We suggest a pushbutton mechanism that facilitates vertical displacement of central Tenerife part, which has high topography and is of higher density than peripheral parts of the island. Beneath Teide, at a depth of 5 km, a low Vp, low Vs, high Vp/Vs anomaly may represent an intermediate phonolitic reservoir. Two similar anomalies at shallower depths may represent the uppermost magma reservoirs directly responsible for phonolitic eruptions. Basaltic eruptions along the three radial ridges appear to be directly fed from mantle sources that appear as high Vp/Vs anomalies. This article is protected by copyright. All rights reserved. We constructed a highresolution seismic velocity model extending to 20 km depth beneath Tenerife. The velocity model shows a crustal thickness of up to 17 km below the Las Caadas caldera and 10 km below other parts of the island. The reservoir of phonolitic magma is revealed as an anomaly of low Vp, low Vs, and high Vp/Vs at 5 km depth. We constructed a highresolution seismic velocity model extending to 20 km depth beneath Tenerife. The velocity model shows a crustal thickness of up to 17 km below the Las Caadas caldera and 10 km below other parts of the island. The reservoir of phonolitic magma is revealed as an anomaly of low Vp, low Vs, and high Vp/Vs at 5 km depth.