This work reports the effect of uniform magnetic field on the heat transfer behavior in the natural convection of electrically conducting but non-magnetic nano-particle suspensions. The experiments are carried out in a differentially heated cubical cavity with two opposite vertical faces at a different uniform temperature kept in a uniform magnetic field. The Rayleigh number range for the present experiment is between 1 × 106 and 1 × 107. To investigate the effect of volume fraction and the type of nanofluid, three different volume fractions of multi-wall carbon nanotubes, graphene, copper, and silica nanofluid are tested at different strengths and directions of the magnetic field. The presence of magnetic field deteriorates the heat transfer which depends upon the direction, strength of the magnetic field and type, and volume fraction of the nanofluid used. The role of magnetic field in the suppression of heat transfer in the presence of magnetic field is explained by a theory involving the interaction of moving electrically conducting particles with the uniform magnetic field. © 2019 Author(s).