Iraz and Turrialba are a twin volcanic complex that marks a distinct stop in volcanism along the Central America volcanic arc. We present a new travel-time velocity model of the crust beneath Iraz and Turrialba volcanoes, Costa Rica, and interpret it considering the results of previous ambient noise tomographic inversions. Data were acquired by a temporary seismic network during a period of low activity of the Iraz-Turrialba volcanic complex in 2018-2019. Beneath the Iraz volcano, we observe low P-wave velocities (VP = 5 km s-1) and low velocity ratios (VP/VS = 1.6). In contrast, below the Turrialba volcano, we observe a low S-wave velocities (VS = 3 km s-1) and a high VP/VS (= 1.85) anomaly. We found that locations of low VP and VS anomalies (- 15 per cent) correspond well with shear wave velocity anomalies retrieved from ambient noise tomography. At shallower depths, we observe high VP and VS anomalies (+ 15 per cent) located between the summits of the volcanoes. Sub-vertical velocity anomalies are also observed at greater depths, with high VP and VS anomalies appearing at the lower limits of our models. We propose a complex structure of an intermediate magmatic reservoir, presenting multi-phase fluid states of a liquid-to-gas transition beneath Iraz and a juvenile store of magmatic fluid beneath Turrialba, while shallow fluid transport provides evidence of magmatic-hydrothermal interactions.