Floating microcarriers were prepared from a sodium alginate solution containing CaCO3 and NaHCO3 as gas-forming agents. The solution was dropped to 5% CaCl2 solution containing 10% acetic acid for CO2 gas and gel formation. The effects of gas-forming agents on microcarrier size and floating ability were investigated. As concentration of gas-forming agents increased, the size and floating ability also increased. Microcarrier’s surface and cross-sectional morphology were examined with Scanning Electron Microscopy. NaHCO3 significantly increased porosity and pore diameter than CaCO3. Incorporation of CaCO3 into alginate solution resulted in smoother microcarriers than those produced with NaHCO3 as well as it showed high drug entrapment. Microcarriers incorporating CaCO3 exhibited significantly increased gel strength over control and NaHCO3-containing samples. Releasecharacteristics of Metformin hydrochloride as a model drug was studied in -vitro. Release rate of Metformin hydrochloride increased proportionally with addition of NaHCO3. However, increasingweight ratios of CaCO3 did not appreciably accelerate drug release. The results of these studies indicate that CaCO3 is superior to NaHCO3 as an effervescent agent in alginate microcarrier’s preparations. The enhanced buoyancy and sustained release properties of CaCO3-containing beads make them an excellent candidate for floating drug dosage systems (FDDS).