This study examined the relationship between public expenditure and economic growth in Nigeria from 1981 to 2021 using linear and non-linear autoregressive distributed lag (ARDL and NARDL) bounds models based on Wagner's law and Keynes's hypothesis. The results showed the presence of a long-term relationship between government expenditure and economic growth, with evidence of both linear and nonlinear relationships. The study also found evidence of short and long-run asymmetric impacts of government spending and economic growth, possibly due to various government policies and economic events. The study confirmed the validity of Wagner's law, which suggests a unidirectional causality from economic growth to government spending, while Keynes's hypothesis was supported by evidence of a unidirectional causal relationship running from government expenditure to economic growth. The study recommends that fiscal authorities consider the presence of asymmetries in the adjustment processes of government expenditure and economic growth when formulating fiscal policies to promote economic growth and development.