In recent years, in association with progress and innovation in the field of pharmaceutical technology, there has been an increasing effort to develop sustained release dosage forms for many drugs due to its advantages in safety and efficacy over immediate release drug products. In this investigation matrix tablets of Metformin hydrochloride are formulated using Water hyacinth powder and its rate retardant activity is studied. Tablets were prepared using wet granulation method with different concentrations of Water hyacinth powder. Fourier Transform Infrared Spectrophotometer (FTIR) Differential Scanning Calorimetry (DSC) studies were performed and Surface morphology of the particle was evaluated by scanning electron microscopy (SEM). The drug release patterns were explained in different kinetic models. The study reveals that, Water hyacinth powder can be used as a matrix forming material for preparing sustained release matrix tablets. There is no previous research regarding water hyacinth as rate retarding polymer in drug delivery system. As water hyacinth is easily available in different areas of Bangladesh, so it will be cost effective to be used as a sustained release polymer.