Resistivity imaging using magnetotelluric (MT) method in high-enthalpy geothermal systems is an effective tool to identify conductive clay layers that cover the geothermal systems and to detect a potential reservoir. In this paper, we use MT data from Aluto-Langano geothermal field, a high-enthalpy geothermal field in Ethiopia with the objective of constructing a 3-D resistivity model of the subsurface to better understand the hydrothermal system of the area by correlating it with geology, alteration information from wells and a conceptual model of a high-enthalpy field. In particular, identifying the low resistivity zone associated with clay alteration zones (the cap rock) and delineating potential reservoir are the main tasks in this study. The result of the 3-D inversion identifies three main resistivity structures: a high-resistivity layer associate with unaltered volcanic rocks at shallow depths, a low-resistivity layer related to argillic alteration clay products, predominantly smectite and a gradually increasing high resistivity region at greater depths related to the formation of high-temperature alteration minerals such as chlorite and epidote. The recovered resistivity model corresponds very well with the conceptual model for high-enthalpy volcanic geothermal systems where an increase in resistivity below a highly conductive surficial layer (clay cap), reflect an increase in temperature with depth. This is a common signature of high-temperature geothermal systems.