Disease estimates from surveillance in mixed health systems is affected by lack of data from the private sector. We aimed to characterize private sector engagement and reporting to a disease surveillance network, and determine the implications on dengue case detection. We developed and set up a public–private network (CODREN—Community Disease Detection and Response Network) with recruitment of eligible health resources ( n = 462) in a municipal ward of Pune city, India (population 209,331). Dengue cases reported through CODREN were compared with reports of the local dengue surveillance (LDS) over 1 year. Private clinics constituted the majority of eligible providers (60%, 276). Retention of participants was 81.7% with 13.9% reporting dengue cases. Phone call was the preferred reporting method (85.5%, 564 reports). CODREN captured a higher number of cases than LDS (78.9%, 251 vs 50.6%, 161), increasing case detection by 18% due to increased private reporting points. A twofold lower number of cases was reported by LDS from shared reporting points with CODREN, due to discrepancies in case definitions and diagnostic test preferences among private providers. We conclude that private sector engagement can improve dengue case detection with the selective inclusion of providers, sustained contact, feedback and simple reporting methods. Testing guidelines and case definitions adopted by the LDS need to address heterogeneity of private practice in mixed health systems, in order to improve dengue estimates in India.