Hyland, Lee, and Mills (2015) specified the two most popular scales for mindfulness: the Freiburg Mindfulness Inventory (FMI; 30 items, Buchheld, Grossman, & Walach, 2001; 14 items, Walach, Buchheld, Buttenmüller, Kleinknecht, & Schmidt, 2006) and the Mindfulness Attention and Awareness Scale (MAAS; Brown & Ryan, 2003). However, the popularity of these measures does not necessarily mean that they are of high quality. Especially considering the complex epistemology and ontology of the mindfulness construct, we should apply mindfulness assessments with caution. More specially, according to item development theorists in the industrial and organizational (I-O) area (see Hinkin, 1998; Hinkin & Tracey, 1999; Kerlinger & Lee, 2000; Schriesheim, Powers, Scandura, Gardiner, & Lankau, 1993), scholars must select measures that have (a) a clear operational definition; (b) alignment between definition and measure (content validity); (c) high reliability and (d) high construct validity; and (e) high criterion-related validity. However, it is not clear which of the available mindfulness assessments satisfies these criteria and to what extent. In this commentary, we assess currently used measures based on these criteria and provide directions for future research.