This paper describes the first Text-to-Speech (TTS) system for the Mongolian language, using the general speech synthesis architecture of Festival. The TTS is based on diphone concatenative synthesis, applying TD-PSOLA technique. The conversion process from input text into acoustic waveform is performed in a number of steps consisting of functional components. Procedures and functions for the steps and their components are discussed in detail. Finally, the quality of synthesised speech is assessed in terms of acceptability and intelligibility.