Egypt experiences a shortage of water for agriculture. Since spearmint is a significant plant that uses a lot of water, an enhanced management strategy for crop irrigation is required. Soil additives with organic matter could be a potential way to boost spearmint (Mentha spicate L.) water productivity. Over the course of two growing seasons, a field experiment was established under newly reclaimed soil. This is to elucidate the influence of biochar, compost, and their combination application under different irrigation water levels (120, 100, and 80% of crop evapotranspiration “ETo”) on spearmint yield, quality, and irrigation water productivity. The results of a split-plot designing experiment indicated that applying different soil additives and irrigation water levels significantly affected the studied parameters. However, meaningfully higher fresh herb yield (6.4 and 7.79 ton/ha) was recorded in the treatment receiving biochar mixed with the compost under 120% ETo in both seasons. Also, biochar mixed with compost offered the highest values of the essential oil main component; carvon under 80% ETo. Moreover, results showed that biochar and compost had favorable effects on spearmint production by boosting leaf chlorophyll content and increasing nutrient absorption. In both seasons, data revealed that spearmint water productivity under 80% ETo was reduced by 18.28% and 7.92% relative to 100% ETo as well as 23.17% and 24.75% compared to 120% ETo using biochar combined with compost. Using a combination of compost and biochar is suggested as an extremely efficient way to boost spearmint yield and water productivity.