The aim of this paper is to develop sustainability composite indices to evaluate sustainability reporting and performance of companies using their reported indicators. This study used data collected from a survey, content analysis and study the sustainability reports of companies that used global reporting initiatives indicators. The sustainability composite indices developed in this study consists of both a uniform system of weights and reported measures of the GRI indicators in sustainability reports. First, the level of importance of indicators were identified using a survey from 240 Australian and New Zealand companies in different industries. The sustainability reports of sample companies in both a highly-polluted industry (mining and metal sector) and a non-highly polluted industry (financial services sector) which had applied the GRI standard in their reports for the period of 2011 to 2014 were also studied. The content analyses of the sustainability reports of sample sectors showed the level of reporting of the GRI indicators in these companies. A sustainability disclosure index (SDI) was developed using the uniform system of weighting and level of reporting of indicators. The sustainability measures were also collected from study the sustainability reports of these companies. A sustainability performance index (SPI) was also developed using a uniform system of weights and normalised measures collected from the sustainability reports of the sample sectors over the study period. The developed composite indices have the capacity of conducting both cross-sectional and longitudinal comparisons among companies in the same or different industries across a period of time. Results of the analyses showed that in mining and metals companies, there was a positive relationship between number of reported indicators and sustainability performance which aligns with economic theories for voluntary reporting. However, in financial services, companies with lower sustainability performance reported more and in more details which is implied by socio-political theories for voluntary reporting. The study contributes models and approaches to develop indices for evaluating sustainability disclosure levels and sustainability performance and evidence is provided for a relationship between sustainability disclosures and performance.