Abstarct: In this study convective heat transfer over two heated wall-mounted cubes in three dimensional steady state laminar incompressible fluid flow by Cu-Water nanofluid az a cooler is investigated. Two cubes are under constant heat flux and placed in different tandem and staggered arrangements on a adiabatic baxse plate. Itʼs used finite-volume method and SIMPLE algorithm to solve continuity, momentum and energy equations for nanofluid that its effective thermal conductivity is dependent on temperature. This subject is studied for different streamwise (L) and spanwise (m) distances between two cubes and and .Effects of these parameters are considered on streamlines and drag coefficient as flow characteristics and also distribution of temperature on the baxse plate and all surfaces of two cubes and local and average Nusselt number as thermal characteristics.The results show that the temperature distribution is strongly dependent on flow structure and varies with any change of flow pattern in different cubes arrangements. In addition it is observed drag coefficient which is influenced more by pressure forces, in staggered arrangement is more than tandem arrangement, because there are more large complex vortices around two cubes in this arrangement. The vortices hold in heat of warm surfaces of cubes; Therefor heat transfer on part of surfaces near more complex vortical region that are more complex is fewer than other part of surfaces. Moreover, Itʼs observed amount of heat transfer increased with adding nanoparticles to the baxse fluid and increasing particle volume fraction.