||The mini-emulsion polymerizations of styrene in the presence of carboxyl acid functionalized and non-functionalized RAFT agents were carried out using conventional surfactant (sodium dodecyl sulfate; SDS) and a water-soluble and oil-soluble initiators such as potassium persulfate (KPS) and 2.2'-azobisisobutyronitrile (AIBN). The influence of the different initiators, existence of carboxylic acid moiety, and varying concentration of the RAFT agent on molecular weight, molecular weight distribution, particle size, and zeta- potential was studied. It was found that the increased concentration of the RAFT agent resulted in the lower molecular weight and molecular weight distribution. The stability of the PS latex was enhanced with an increase in RAFT agent concentration in the case of using KPS and RAFT agent bearing carboxylic acid moiety. In addition, KPS-added system led to faster conversion, lower molecular weight, and the polydispersity index, however, produced similar particle size and its distribution to those of AIBN-added system.