Semiconductor packages including a heat spreader and methods of forming the same are provided. The semiconductor packages may include a first semiconductor chip, a second semiconductor chip, and a heat spreader stacked sequentially. The semiconductor packages may also include a thermal interface material (TIM) layer surrounding the second semiconductor chip and directly contacting a sidewall of the second semiconductor chip. An upper surface of the TIM layer may directly contact a lower surface of the heat spreader, and a sidewall of the TIM layer may be substantially coplanar with a sidewall of the heat spreader. In some embodiments, a sidewall of the first semiconductor chip may be substantially coplanar with the sidewall of the TIM layer.