In this study, the effect of rectangular Finlets on the trailing edge noise of a flat plate in an incompressible turbulent boundary layer with Mach number 0. 06 has been studied numerically. The Finlets are modeled upstream of the trailing edge of the flat plate with two spanwise spacing of 1. 5 and 0. 9 mm. Large-eddy simulation (LES) approach with Lund inflow generation model in open-source code of OpenFOAM has been used to simulate the turbulent boundary layer flow. Probe utility has been used for pressure and velocity data acquisitions. The Finlets have increased the PSD of pressure fluctuations in the low to mid frequencies and decreased it at high frequencies between and downstream of the Finlets. Also, the spanwise length scale of the pressure fluctuations increases, but the eddy convection velocity is reduced and their effects have been intensified by the reduction of the spanwise spacing. The mean velocity decreases, but the turbulence intensity increases downstream of the Finlets. The reduction of the spanwise spacing of the Finlets results in the formation of a stronger shear layer and the extension of the shear sheltering area downstream of the Finlets. According to the results of the far-field noise prediction with Curle analogy, Finlets with the spacing of 1. 5 mm have slightly reduced the noise about 0. 3 dB but the Finlets with the spacing of 0. 9 mm have increased the trailing edge noise of the flat plate about 1. 0 dB.