The dramatic growth in urbanization and population in Riyadh, Saudi Arabia have brought some environmental challenges that need to be efficiently dealt with. One of these challenges is finding the proper management for hugely produced municipal solid wastes (MSW). Recycling of MSW via composting is a possible option of its management and has recently received more attention, although compost ability and chemical characteristics of resulting compost are not widely studied. Therefore, the aim of this study was to evaluate the characterization of the municipal organic wastes fraction and composting process. In this study, the organic fraction of MSW was composted alone or with a chemical and/or organic additives using a windrows composting system for a period of 12 weeks. Changes in temperature, EC, pH, C/N ratio, total contents of Zn, Fe, Mn, Cu, Cr, Cd, and Pb were monitored over a regular interval throughout the composting process. All the measured parameters showed great differences among types of compost. The results indicated that medium temperature range was 33-64ºC, EC was 2.85-4.50 dS m^-1, and pH was 7.50-8.50. Moreover, C/N ratio was found within the acceptable average range (8.0-15). The produced composts contained a high level of total N (1.80 %), total P (0.50 %), and total K (0.25 %). The total contents of Zn, Fe, Mn, Cu, Cd, Cr, and Pb were within the permissible limits for compost.