Psychological measurement and theories face a constant proliferation of allegedly new constructs and scales, leading to numerous semantic overlaps between these. Additionally, common-method variance can be responsible for construct overlap, which itself can be influenced by respondents' affectivity and mood. The construct of mindfulness may also be affected by such phenomena, as its boundaries are not yet clearly defined and because it shows noticeable conceptual overlap with other constructs, like the Big Five, emotion regulation, or mental health. This study examined semantic and sentiment similarities between widely used scales assessing mindfulness (FFMQ, FFMQ-S, KIMS, MAAS), the Big Five (NEO-PI-R, NEO-FFI, BFI), emotion regulation (ERQ, CERQ, PANRS), and mental health (SCL-90, BSI-53, BSI-18, STAI, PANAS, BDI-2, PSS, PSWQ). Construct overlap was assessed via latent semantic analysis, sentiment analysis, and a qualitative content analysis. Mindfulness scales showed high construct overlap among each other (semantic and sentiment similarity: 0.93 and 0.63) and the Big Five (0.85 and 0.64), as well as substantial construct overlap with emotion regulation (0.84 and 0.51) and mental health scales (0.74 and 0.42). These findings suggest that semantic and sentiment similarities contribute to the high correlations of mindfulness measures with these other measures observed in extant research.