Abstract: Environmental conservation in the world presents a daunting task due to population increase. In Tanzania, environmental degradation has occurred at an alarming rate in specific areas including Tabora. The continued burgeoning of the human population has resulted in changes in land use, increasing demand for resources and excision of forests. This study employed the theory of planned behaviour to predict on-farm tree planting behaviour of farmers. A sample size of 288 farmers drawn from Nzega and Sikonge districts in Tabora region was interviewed to measure standard theory of planned behaviour constructs. The data and hypotheses were examined using structural equation modeling performed in partial least squares algorithms. Results from the maximum likelihood estimation showed that attitudes, subjective norms and perceived behavioural controls were significantly and positively associated with stronger intention and related to farmers’ behaviours in farming decisions. Farmers saw hindrance in tree planting operations being a result of cultural beliefs which yielded negative impacts. However, these were outweighed by perceptions of positive impacts. The drivers of these constructs can be harnessed by policy makers by directing farmers’ intentions and behaviours toward conserving and sustaining fragile eco-environmentally areas against a threatening population growth in the region through agroforestry uptake programs.