Provided are a package structure and a method of forming the same. The package structure includes a first die, a second die group, an interposer, an underfill layer, a thermal interface material (TIM), and an adhesive pattern. The first die and the second die group are disposed side by side on the interposer. The underfill layer is disposed between the first die and the second die group. The adhesive pattern at least overlay the underfill layer between the first die and the second die group. The TIM has a bottom surface being in direct contact with the first die, the second die group, and the adhesive pattern. The adhesive pattern separates the underfill layer from the TIM.