PhD. (Environmental Management) / Climate change and variability has rapidly emerged as one of the most serious threats to sustainable development especially for developing African countries such as Rwanda. Since most of the agricultural activities in African countries are rain-fed, any adverse change in climate is likely to have a devastating effect on output and the livelihood of the majority of the population in the affected countries. Therefore, there should be continuous and regular preparedness to on-going climate variability. Climate change and variability derived information, are most likely to improve the agricultural outcomes when it is integrated into a framework for decision making to mitigate specific risks. It is in that regard, this research aims at analyzing climate change and variability and their impacts on the yields of major food crops in Rwanda. The raw climatic data (temperatures and precipitations) used in this study were obtained from the Rwandan Meteorological Center based in Kigali and Rwanda Environment Management Authority (REMA) while the agricultural records were collected from the National Institute of Statistics of Rwanda (NISR) and the Ministry of Agriculture and Animal Resources (MINAGRI). Length and completeness of records were the basic criteria used to select weather stations in order to have the most complete dataset. Five major crops, namely beans, cassava, Irish potatoes, maize, and sweet potatoes were selected for investigation because they are grown over large areas in most parts of the country during the two agricultural seasons i.e. season A (September-January) and season B (February-June). This research uses a number of statistical techniques in an attempt to quantify the magnitude and significance in temperature, rainfall, number of rainy days, aridity index and rainfall erosivity changes and variability taking place over Rwanda. The same techniques were applied in determining the magnitude and significance of inter-annual variations in food crop yields over Rwanda. A geographical information system (GIS) was used to present spatially the results on maps...