A nanofluid is composed of a base fluid with a suspension of nanoparticles that improve the base fluid’s thermophysical properties. In this work, the authors have conducted experimental tests on an alumina-based nanofluid (Al2O3/H2O) moving inside a 3D-printed lattice channel. The unit cell’s lattice shape can be considered a double X or a double pyramidal truss with a common vertex. The test channel is 80 mm long and has a cross-sectional area, without an internal lattice with that has the dimensions H × W, with H = 5 mm and W = 15 mm. A nanofluid and a lattice duct can represent a good compound technique for enhancing heat transfer. The channel is heated by an electrical resistance wound onto its outer surface. The heat transfer rate absorbed by the nanofluid, the convective heat transfer coefficients, and the pressure drops are evaluated. The experimental tests are carried out at various volumetric contents of nanoparticles (φ = 1.00%, φ = 1.50% and φ = 2.05%) and at various volumetric flow rates (from 0.2 L/min to 2 L/min). The preliminary results show that in the range between 0.5 L/min ÷ 2.0 L/min, the values of convective heat transfer coefficients are greater than those of pure water (φ = 0) for all concentrations of Al2O3; thus, the nanofluid absorbed a higher thermal power than the water, with an average increase of 6%, 9%, and 14% for 1.00%, 1.50% and 2.05% volume concentrations, respectively. The pressure drops are not very different from those of water; therefore, the use of nanofluids also increased the cooling efficiency of the system.