This study examined the relationship between tax revenue, external debt, and infrastructural development in Nigeria, with a focus on government expenditure in agriculture, transport, and communication. The objectives were to determine how external debt affects government expenditure on agriculture and transport/communication. Using secondary data from 2000–2022 sourced from the Central Bank of Nigeria and World Bank, regression analysis was applied. The findings revealed that external debt had a significant effect on agricultural expenditure (β = 0.421; p = 0.012) and an even stronger effect on transport and communication expenditure (β = 0.537; p = 0.004). The study concluded that while external borrowing positively impacts infrastructure, the transport and communication sector benefits more than agriculture. It recommended prudent debt management, equitable allocation of funds, stronger tax reforms, and enhanced accountability. These measures will ensure sustainable infrastructural growth and reduce fiscal vulnerability.