This paper presents part of a broader, large-scale study regarding educational leadership towards inclusive education of disabled students in Greece, highlighting the school principals’ potentially decisive role. Specifically, it investigates Greek school principals’ knowledge, beliefs, attitudes and practices regarding the inclusive education of disabled students in their school-units, as well as their values, examining a) whether there are statistically significant correlations between the aforementioned variables, b) and between these and the school principals’ socio-demographic and professional characteristics. The data were collected through an original questionnaire validated for the Greek context, that was electronically administered to a representative stratified sample of 582 school-principals from 334 primary and 248 secondary Greek schools. The results indicate multiple and multi-layered relationships between the examined variables; and most notably that specific values (benevolence, universalism, self-direction & stimulation) promote the implementation of inclusive education while others (security, tradition, conformity, achievement & power) hinder it. Understanding the relationships between school principals’ knowledge, beliefs, attitudes and practices regarding the education of disabled students and their values may contribute significantly to the promotion of inclusive education. However, the direction and strength of these relationships needs to be further explored to shed more light on the influence of educational leadership.