Besides its paramount role to life and human survival on the earth, water also plays a crucial role in understanding certain earth processes. Water can be quite hazardous, whether in a surplus state or in a deficit state. The former presents as flood, while the latter presents as drought. Nigeria, unfortunately, over the years has been shown not to be immune to both extreme states of water. It is, therefore, crucial to continually monitor the state of water in order to mitigate whatever danger both states may present to the nation. One key index for measuring the quantity of water on land is the Terrestrial Water Storage (TWS), which incidentally is obtainable from gravity data of the Gravity Recovery and Climate Experiment (GRACE) satellite mission. This study leverages on the availability of GRACE mascon data to give insight into the dynamics of TWS within Nigeria. The study observed an increasing trend of TWS in all hydrological areas and basins within Nigeria. Trends of up 10mm/year were observed in the Sokoto-Rima basin. The flash and fluvial flooding events of 2012 and 2015, were captured by GRACE satellites. In terms of its seasonal fluctuations, TWS values are relatively minimal in the first 6 months of the year and maximal in the remaining 6 months. Its peak value is usually observed around October of each year. A clear inter-annual pattern is also observed in peak values of TWS within the period of study (2002–2017).