A trim strip for the edge of a window channel for an automotive side window which is adapted to be lowered into the window channel. The trim strip includes a rigid fixing profile having a U-shaped housing, an at least partly rubber elastic seal having a seal lip cooperating with the side window and a seal profile which is adapted to be inserted into the housing, and at least one groove which is arranged in the U-shaped housing and which is provided with at least one undercut portion that is engaged by a rib arranged on the seal profile. The groove is arranged in the transverse web of the U-shaped housing. Thus, the trim strip permits an easier introduction of the seal profile in the fixing profile and a secure retention of the seal profile in the fixing profile.