The Lattice Boltzmann Method (LBM) is applied to computationally investigate the laminar flow and heat transfer of an incompressible fluid with constant material properties in a two-dimensional channel with a built-in triangular prism. Not only the momentum transport, but also the energy transport is modeled by LBM. A uniform lattice structure with a single time relaxation rule is used. The flow is investigated for different Reynolds numbers, while keeping the Prandtl number at a constant value of 0.7. The results show how the presence of a triangular prism affects the flow and heat transfer patterns for the steady-state and unsteady/periodic flow regimes. As an assessment of the accuracy of the developed LBM code, the results are compared with those obtained by a commercial CFD code. It is observed that the present LBM code delivers results that are of similar accuracy to the well-established CFD code.