The paper examines the causal relationship between FDI and economic growth (GDP) in thirteen ECOWAS countries using both time domain and frequency domain testing procedures using annual data from 1970 to 2015. The results showed that time domain is not adequate in detecting causality. The time domain detected causality in only four out of thirteen countries whilst the frequency domain detected causality at different frequencies and cycles in nine out of thirteen countries. The findings of this study indicate the importance of frequency domain causality, that it decomposes causality at different frequencies and subsequently detects causality at certain cycles lengths. The general observation that economic growth leads FDI calls for ECOWAS leaders to rethink about painful sacrifices they make to attract FDI into the region.