A bathtub seat system a bathtub that has a bottom wall and a perimeter wall that is attached to and extends upwardly from the bottom wall. The perimeter wall includes a pair of lateral walls attached to and extending upwardly from the bottom wall. The perimeter wall has an upper edge defining an opening extending into the bathtub. A block is removably positioned in the bathtub and has a bottom side, a top side and a peripheral surface extending between the top and bottom sides. The peripheral surface includes a front side, a back side, a first lateral side, and a second lateral side. A width of the block from the first lateral side to the second lateral side increases from the bottom side to the top side. The block extends between and frictionally engages the lateral walls. The block provides a seating space for a person using the bathtub.