The work of James F. Masterson (1926-2010) has extended over more than 5 decades and has influenced countless clinicians in treating the various disorders of self (borderline, narcissistic, schizoid). The exclusive aim of the current paper to describe the developmental self and object-relations approach of James Masterson in conceptualising and treating the Borderline Disorder of Self. Special attention will be given to the use of clinging, distancing, and focusing on the other as borderline defences. The therapeutic frame and the concept of the borderline triad, that is, self-activation leads to anxiety that leads to defence will also be explored.