The study on Indigenous Knowledge of Tribals of Pachaimalai hills, was conducted to study the constraints experienced by the tribal farmers in adopting the indigenous agricultural practices. The study was conducted in Pachaimalai hills of Trichy district. A sample of one hundred tribal farmers (respondents) was selected from the tribal hamelets using proportionate random sampling technique. Nearly twenty one indigenous agricultural practices were identified in the crops like paddy, tapioca and sorghum. In addition ten common indigenous agricultural practices were also identified. The data were collected with the help of well structured and pretested interview schedule and suitable statistical tools were used to analyses the data. The important constraints reported were ‘no reward for indigenous agricultural practices by Government Officials’, ‘youth’s preference for urban life,’ ‘Lack of documentation’, and ‘poor income from agriculture’.