Interventive Psychodiagnosis, is not just an effective clinical practice, it is also a valuable scientific research procedure. Although it has a well-established status as a clinical intervention, there are few studies regarding its potential as a research method. In view of this situation, the present essay aims to accomplish a preliminary analysis of the quality of knowledge produced by Therapeutic Assessment, concerning its validity and reliability, as well as the means to assess them. The study also supports the possibility of obtaining objective knowledge from Therapeutic Assessment, in spite of the influence of researcher’s subjectivity on the results of the work. In this sense, the researcher ethical conduct and his/her capacity to identify himself/herself with the participant play an essential role. Finally, some trends of psychoanalytical thought, particularly the kleinian and winnicottian theories are presented, as they can support this clinical/scientific procedure in order to preserve its epistemological integrity.