Background: Despite significant reduction in global disease prevalence, leprosy still has a high rate of disability while its determinants are unfair and many of them are amendable. The objective of this study was to measure inequality of disability in leprosy in Iran.Methods: This was a cross-sectional study (2006-2007) on all living people affected by leprosy registered in W. Azerbaijan province health center, Western North of Iran. The outcome of the study was the socio-economic inequality considering presence or absence of grade 2 disability (G2D) based on the WHO classifications. An extended concentration index decomposition approach was used for analysis.Results: Among 452 cases, 65.3% were male and 67% were affected by the multi bacillary type. Overall G2D was 65.3%. The estimated Concentration Index was −0.0782, showing presence of pro-poor socio-economic inequality of G2D, while extended CI estimation (v=5) was −0.163. Achievement index with coefficient (v=5) revealed that G2D mean was 16% more than classic mean in the poorest group. The result of decomposition of the existing inequality revealed that, some of the determinants such as receiving mono-therapy, education, urbanization, and bacillus calmette guerin (BCG) vaccination had shared contribution (67.4%, 61.8%, 59.2%, and 57.5% respectively).Conclusions: This study provided new perspective for the health system to leprosy control considering the significant gap between rich and poor (inequality) regarding G2D disability, and its effective elements in socio-economic strata. Some effective actions can be considered to reduce the scale of existing inequality.