The purpose of this chapter is to present a sociocultural-informed, evidence-centered design (SCI-ECD) model for designing and validating multidimensional assessment instruments of engineering competencies. This chapter also aims to guide assessment developers and researchers in engineering education. First, the chapter discusses the need to assess multidimensional learning in engineering based on the global demand for engineers who can integrate content knowledge with engineering practices and technical skills from multiple domains simultaneously. Then, the chapter briefly discusses foundational concepts of assessment, including validity, reliability, and fairness, with an emphasis on the latter. Next, the chapter describes SCI-ECD’s layers and decisions associated with its use, providing examples to illustrate its application to the design of engineering competency assessments for culturally and linguistically diverse test-takers. To conclude, the chapter discusses future directions for research based on the SCI-ECD model.