In Singapore and in elsewhere alike, educators nowadays are paying much more attention on the set of teaching and assessment recommendations called the 21st century skills that include creativity at the policy, programmatic, school and classroom levels. As these education systems develop and respond to the demands of the new century, educators are facing many challenges. In general, educational assessment does not pay much attention to creativity. This is despite the global call for teaching and learning of 21st century skills. There are many reasons to this phenomenon and it can be understood from the conceptual and practical level. At the conceptual level, there is indeed a dearth of research on how creativity can be assessed in language art writing. Teachers think that assessments of creativity writings are too subjective to make a fair judgment. That could be one of the many reasons why both formal and informal assessments of students' creativity writings are rare in Singapore and in elsewhere. In educational assessment terminology, this concerns the concepts of validity and reliability issues of assessing students' creativity in writings. Teachers find it challenging to design valid and conduct reliable assessment to assess students' creativity. Nevertheless, this article argues that if creative writings are valued in the 21st century education, then valid and reliable assessment methods should be introduced in the language art education. In other words, the technical quality of assessing students' creative writings should be ensured. Using Singapore secondary school Chinese Language curriculum and assessment as an example, this article further illustrates and discusses the possible solutions to overcome these challenges in the assessment of creative writing.