Extension and Advisory Services (EAS) have contributed to the overall development of the farming community by getting engaged in a broad spectrum of activities. Although several players such as public, private, and non-governmental organizations offer EAS, FPOs are seen as a significant substitute and add-on to these services as they deliver inclusive EAS that are driven by farmers and serve the purpose of the farmers. In the Indian situation, an effectiveness evaluation study of EAS was measured with the effectiveness index with more general indicators. Against this backdrop, the present research is concerned with the development and application of the Composite Effectiveness Index (CEI) for measuring the effectiveness of extension and advisory services offered by FPOs using a theoretical framework. Birner’s best-fit framework, a globally accepted theoretical framework was used for devising twenty-five indicators under five dimensions. Analytical Hierarchy Process was used for giving weights to dimensions and indicators. Application of this index was carried out on twenty FPOs. FPOs were selected from two districts each in Telangana and the Andhra Pradesh state of India. Two hundred farmers and twenty FPO officials were surveyed and the index score for the pooled sample was 0.66. It showed scope for improvement. The study helped to identify the strong and weak points in the present EAS offered by FPOs and suggested suitable measures. By regressing the index scores with different factors, sex, access to FPO, access to formal credit, training attended, and the number of activities undertaken by the FPOs showed a significant relationship. An inter-temporal and inter-regional comparison of FPOs can be done using the replication of similar studies. The Index can also be utilized for evaluation of EAS provided by other players. Keywords: