This book constitutes the refereed proceedings of the 5th International Conference on User Science and Engineering, i-USEr 2018, held in Puchong, Malaysia, in August 2018.The 32 papers accepted for i-USEr 2018 were selected from 72 submissions with a thorough double-blind review process. The selected papers illustrate how HCI is inclusive and omnipresent within the domains of informatics, Internet of Things, Quality of Life, and others. They are organized in the following topical sections: design, UX and usability; HCI and underserved; technology and adoption; human centered computing; HCI and IT infrastructure; and HCI and analytics.