This paper examines to test the causality relationship between government spending and gross domestic product (GDP) in Saudi Arabia between 2000 - 2017. Moreover, the model aims the validity of Wagners Law as well as Keynes Theory, using the Johansen approach and error correction modelling (VECM). The Augmented Dickey-Fuller (ADF) test show that all selected variables are integrated of order I (1) as well as the outcome from the co-integration of the Johansen test find a long-term relationship between government spending and economic growth. Concrete evidence exists as to the importance of the role of government spending in enhancing economic growth, which supports the Keynesian's hypothesis.