Children with dyslexia may have adequate cognitive abilities but they often show considerable difficulties in reading where they are less accurate in spelling and pronouncing words. Phonological deficit is the main cause of reading disorders in dyslexic children, and hence, developing competence in phonological awareness is important to increase children's sensitivity to the structure of a word. This study aims to develop a web-based assistive technology called Lexiroom for Indonesian dyslexic children to increase their phonological awareness. This includes the aspects of syllable awareness, segmenting words into sounds, and manipulating sounds. As a preliminary study, the proposed learning media is implemented using a single subject design with a research and development approach. The results show that Lexiroom can improve the phonological awareness of a child diagnosed with dyslexia. However, Lexiroom still has limitations in doing speech recognition, so in making the next media it is necessary to consider the structure in speech recognition assets to minimize error answers that are inputted in the form of voice.