Two species of cyanobacteria, such as Anabaena variabilis and Hapalosiphon sp. were collected from the various agro-climatic regions of Warangal district of Telangana state. Purified isolated culture were inoculated in 500ml Erlenmeyer flask containing 100 ml BG-11 N+ media. The cultures kept under optimum conditions and routinely sub-cultured. The impact of herbicides such as 2,4-D, Excel Mera were studied two filamentous cyanobacteria with reference to Chlorophyll-a, Carotenoid, Phycocyanin contents. In Anabaena variabilis the Chlorophyll-a revealed that the lower concentration of 2,4-D (6ppm) on 4^th day has shown some increase when compare with other concentrations (12,18,24ppm) and the Hapalosiphon species at 5ppm concentration on 8^th day expressed with little higher than the other concentrational under study.