Imperata cylindrica, a widespread invasive weed, is significantly disrupting plantations and degraded hill forests in Bangladesh through the release of allelopathic chemicals that inhibit the growth of other plants. To assess its allelopathic impact, an experiment was conducted using six concentrations of Imperata cylindrica leaves extract (prepared at 28–30°C) to evaluate effects on seed germination and seedling growth of four forest tree species: Syzygium fruticosum (Putijam), Albizia procera (Silkoroi), Azadirachta indica (Neem), and Ficus hispida (Dumur). The extracts’ lower concentrations (<20 g/L) stimulated germination in S. fruticosum and A. indica, while concentrations above 20 g/L inhibited germination of all species. Increasing concentrations negatively affected shoot growth, particularly of F. hispida, and root growth of A. indica. Among the tested species, A. procera showed the highest vigor index for both root and shoot growth at the 50 g/L concentration, indicating a higher tolerance to I. cylindrica allelopathy. In contrast, F. hispida was the most adversely affected. These findings suggest that A. indica and A. procera are more resilient to the allelopathic effects of I. cylindrica and could be promising candidates for reforestation or afforestation in areas heavily infested with Imperata cylindrica. However, greenhouse studies and field studies are needed for drawing definitive conclusions.