We have made a first investigation on the annihilation rates of the positronium negative ion (Ps(-)) embedded ill dense plasma environments. We have also estimated the energies and other bound state properties of Ps(-) ion in the dense plasma background. Debye screening model has been used to consider plasma effect on the potential energies of the charged particles. Correlation effects between the charged particles are taken care of using a multi-term correlated basis sets. The one-, two- and three-photon annihilation rates and the ground-state energies of Ps(-) are reported for various Debye lengths along with the ground-state energies of the Ps atom. (c) 2006 Elsevier B.V. All rights reserved.