Increased interest in paleoenvironmental studies is a result of climatic changes occurring at present and predicted for the future. Such studies could be done using the stable isotope compositions (δ²H and δ¹⁸O) of kaolins, which provide knowledge on the paleoenvironmental conditions prevailing during the time of kaolinisation. In this study, the stable isotopic compositions of clay-size fraction of kaolins occurring in Cretaceous and Tertiary Formations of the Douala Sub-Basin in Cameroon are presented, with the aim of reconstructing the paleoenvironmental conditions of the Sub-Basin. To achieve this, the clay-size fraction (<2μm fraction) of 8 kaolinite-rich samples were analysed for their δ²H and δ¹⁸O compositions, and results were reported as part per mil (‰) relative to the SMOW standard. The δ¹⁸O values of kaolins found in the Cretaceous–Tertiary Formations of the Douala Sub-Basin varied between +18.2 and +21.0‰, whereas the δ²H values varied between –69 and –53‰. Nine of the eleven samples plotted on the right of the supergene–hypogene line. Five of these nine samples plotted very close to the kaolinite line, which represents the composition of kaolinite in equilibrium with meteoric water at 20°C; suggesting a supergene weathering origin of these kaolins. The determination of the temperature of kaolinisation yielded mean formation temperatures of 22±2°C and 27±6°C for Cretaceous and Tertiary kaolins, respectively. Excluding the two samples falling in the hypogene field, averages of kaolinisation temperatures were 20 and 25°C during the Cretaceous and Tertiary periods, respectively. These temperatures are slightly below the present mean annual temperature in Douala (27°C), thereby suggesting that the climate was becoming warmer from the Cretaceous to the Present. Therefore, Douala had a cooler and rainy climate during the Cretaceous, and the climate is gradually becoming hotter and more humid, favouring the refinement of existing kaolins and the kaolinisation of kaolin-forming minerals in the Sub-Basin.