A deployment ramp helps to direct a side airbag to deploy along a desired deployment trajectory from a vehicle seatback to a deployed position adjacent a side structure of the vehicle. The deployment ramp includes a mounting wall configured to be connected to a seat frame of the seatback. The deployment ramp also includes a deployment wall configured to deflect outboard of the vehicle seatback in response to airbag deployment and at least partially cover padding and/or a cover of the seatback. The deployment ramp further includes a bottom wall that extends between the mounting wall and the deployment wall, the bottom wall forming a reaction surface for side airbag deployment in the deployment trajectory.