The management of Nigeria's external reserves, a key indicator of the nation's financial health and ability to withstand economic shocks, is at the centre of this economic investigation. This study investigates the effect of debt servicing on external reserves in Nigeria from the first quarter of 2010 to the first quarter of 2023. An ex post facto research design was adopted for the study. Quarterly time series data for external reserves, external debt servicing, and domestic debt servicing were collected from the Central Bank of Nigeria statistical bulletin and Debt Management Office reports. Philip Perron test was used to test the stationarity of the data and the ARDL test was utilized to determine the presence of a long-run relationship. The Fully Modified Ordinary Least Squares technique was used to test the effect of debt servicing on external reserves in Nigeria. The findings showed that external debt servicing and domestic debt servicing have a significant effect on external reserves in Nigeria. The study recommends that the Nigerian government through the Debt Management Office should emphasize diversification in acquiring external debts by engaging with multiple creditors, including multilateral institutions, bilateral partners, and global financial markets. Also, a strong emphasis should be placed on enhancing domestic revenue mobilization efforts. This can be achieved through fair and effective tax policies, reducing tax evasion, and promoting investments in sectors(like the finance sector)that yield sustainable revenue streams. Increased domestic revenue can alleviate the need for extensive domestic borrowing, thereby reducing the strain on external reserves for domestic debt servicing.