Provided are a package structure having a joint structure and a method of forming the same. The package structure includes: a first under bump metallurgy (UBM) structure disposed on a first dielectric layer, wherein the first UBM structure at least comprises: a barrier layer embedded in the first dielectric layer; and an upper metal layer disposed over the barrier layer, wherein a sidewall of the barrier layer is laterally offset outward from a sidewall of the upper metal layer, and a portion of a top surface of the barrier layer is exposed by the first dielectric layer; and a solder layer disposed on the first UBM structure and contacting the upper metal layer.