Chemical soil stabilisation has been practiced for a long time by adding different additives such as cement, lime and fly ash for improving their physico-mechanical properties. However, few studies related to the soil stabilisation using natural pozzolana (NP), lime (L) or the combination of both were recorded for different applications in civil engineering. An experimental investigation was undertaken to assess the effect of NP (containing 46.4% of silica) on the geotechnical properties of L–stabilised yellow clayey soil (YCS), which was obtained from Algerian East-West highway project. Both the L and NP were added to the YCS at levels of 0–8% and 0–20%, respectively. The prepared samples were tested for Atterberg’s limits, compaction and unconfined compressive strength (UCS). In fact, the prepared specimens were cured for 1, 7 and 28 days, after which they were subjected to UCS test. Based on the obtained results, the physico-mechanical properties of YCS can be successfully improved by using the L alone whereby a further improvement was recorded when adding NP to the L–YCS mixture. Furthermore, it should be noted that the apparent lack of SiO2 for some soils can be adequately supplemented by adding NP which has a high amount of reactive silica. Moreover, because the NP is much cheaper than the lime, the use of NP as a better source of silica is highly recommended for soil improvement and can reduce the construction costs.