In our recent research, we have developed novel CaP-mullite composites for bone implant applications. In order to realize such applications, the in vitro dissolution behaviour of these materials needs to be evaluated. In this perspective, the present paper reports the dissolution behavior of pure hydroxyapatite (HAp) and hydroxyapatite composites with 20-30 wt% mullite in simulated body fluid (SBF). The in vitro dissolution experiments were carried out for different time duration starting from 7 days up to 28 days. XRD and SEM results show almost no dissolution for pure HAp and HAp composite with 30 wt% mullite. However, HAp-20 wt% mullite composite exhibits considerable dissolution after 7 days. The alpha-TCP phase mainly contributes to the dissolution process. Based on the dynamic changes in pH, ionic conductivity, Ca and P ion concentration in SBF as well as microstructural observations of the bioceramic surfaces after various time frames of immersion in SBF, the differences in dissolution behaviour are discussed.