The mindfulness 'foundations' of existential-phenomenology appeared at the turn of the 20th century. Humanistic psychology's affinity with phenomenology emerged in the latter half of the mid-20th century. Yet the cognitive behavioral therapy (CBT) third wave mindfulness literature does not appear to have turned toward full collaborative acknowledgment of its neighboring precursors. A revised history of Western mindfulness-based work and psychology is thus provided. Parallels among phenomenological-humanistic psychology (PHP), dialectical behavior therapy (DBT), and mindfulness-based cognitive therapy (MBCT) are also discussed. Specifically, non-judgmental observation and description, validation, acceptance, intuition, doing and being, bodily mindfulness, letting be, and meaning-making are reviewed. Herefrom, the CBT third wave is invited into generative intra-disciplinary dialogue with PHP.