Assessing complex constructs such as those discussed under the umbrella of 21st century constructs highlights the need for a principled assessment design and validation approach. In our discussion, we made a case for three considerations: (a) taking construct complexity into account across various stages of assessment development such as the design, scaling, and interpretation aspects; (b) cognitive validity evidence that goes beyond traditional psychometric analyses of response patterns, and (c) cross-cultural validity. We analyze the four articles in this special issue with respect to these three considerations and discuss the kinds of evidence needed to support interpretation of scores from 21st century constructs.