Notable dryland expansion from changes in global aridity has been documented in previous studies, particularly with the increase in global mean temperature. Here, we examined the changes in the aridity of the western region of Africa over the past four decades. Using the aridity index (P/PET) as an indicator, the Climate Research Unit (CRU TS) data was used to identify drying and wetting areas of the region. The result showed that intense warming of 0.018 °C per year has occurred which was more evident in the last two decades. The warming in the past two decades caused a significant increase in PET. The first two decades were the driest compared to the last decades, particularly the first decade which also had major drought occurrences across the region. The aridity index increased by 0.86 (x10−3) per year within the past four decades, with the greatest change at the semi-arid zone. Result showed that precipitation exerts dominant control on aridity changes in the region despite a significant increase in PET. This was evident in the expansion of the wet areas between 2000 and 2019 compared to the 1979–1998 period.