The conventional vibration welding process of polyamide 66 only has a continuous and steady melt flow during the quasi-steady phase. The process and resulting welds have been thoroughly investigated. Radiation cross-linking of polyamide 66 with electron beams alters the material's characteristics. Consequently, the resulting energy balance during vibration welding changes and the squeeze flow is impeded. Additionally, this causes the cross-linking to attain a residual stiffness above the crystallite melting temperature, thereby influencing the characteristics of the vibration welding process. Further, higher weld temperatures and a change in meltdown behavior can be observed. This leads to a varied relationship amongst the process, structure, and properties for vibration welding cross-linked polyamide. Hence, weld strengths up to the value of the base material strength are possible. The scope of this article is to investigate the influence of radiation cross-linking on the material characteristics and, by extension, the resulting processing and welding characteristics. Calorimetric, chemical, rheological, mechanical, and optical investigations serve to highlight the influence of radiation cross-linking on the vibration welding process of polyamide 66. POLYM. ENG. SCI., 55:2493-2499, 2015. (c) 2015 Society of Plastics Engineers