Bi2Te3 is well-known for its utility in thermoelectrical applications and more recently as topological insulator. Its nanostructuration has attracted plenty of attention because of its potential capacity to reduce thermal conductivity. Here, we have grown a composite sample made of a Bi2Te3 nanowires (NWs) array embedded in an alumina matrix. We have then performed scanning thermal microscopy (SThM) in a 3ω configuration to measure its equivalent thermal resistance. Using an effective medium model, we could then estimate the mean composite thermal conductivity as well as the thermal conductivity of the NWs to be, respectively, (λC) = (1.68 ± 0.20) W/mK and (λNW) = (1.37 ± 0.20) W/mK, showing a slight thermal conductivity reduction. Up to now, there have been two main techniques reported in literature to evaluate the thermal conductivity of nanostructures: the use of a thermal microchip to probe a single NW once its matrix has been dissolved or the probing of the whole NWs array embedded in a matrix, obtaining the thermal conductivity of the whole as an effective medium. However, the 3ω-SThM presented here is the only technique able to measure the thermal conductivity of single NWs embedded in a matrix as well as the thermal conductivity of the composite locally. This technique is more versatile and straightforward than other methods to obtain the thermal conductivity of nanostructures.