In this paper, an advanced computational framework is presented for integrated simulation of hydroforming effects and welding assembly operations. The finite element procedures take advantages of existing commercial finite element codes such as ABAQUS by employing a series of user-developed interface modules and a unified material constitutive model formulated with internal state variables that are used to track stress/strain histories induced during forming and welding operations. Its applications in design and welding assembly of hydrofomed components are demonstrated with a series of selected case studies. Based on the detailed finite element simulations described in the above, the following important observations can be made: Weld placements are extremely important in order to mitigate the significant cold work effects in hydroforming. This is true for both the seam weld in the tube and assembly welds after hydroforming Final weld residual stresses, particularly within weld heat affected zones (HAZ), are significantly higher than those in conventionally stamped C-channel sections. The residual stress effects on durability should be accounted for by introducing strain history based fatigue assessment procedures Welding-induced distortions can be amplified by re-distributions of hydroforming-induced residual stresses during welding. Proper fixturing and weld design should be used to control such dimensional variations due to the interactions between hydroforming and welding operations.