Purpose <p><i>Curcuma caesia</i> Roxb. of Zingiberaceae family, commonly known as “Black turmeric”, is a rhizomatous perennial herb. Rhizome of <i>C. caesia</i> is used for managing diabetes, high cholesterol, abdominal pain, menstrual disorders, wounds, eczema, psoriasis, jaundice, inflammation, and cancer-related symptoms, in various traditional health care systems. However, information on appropriate preservation methods to retain maximum level of medicinally potential bioactive compounds in <i>C. caesia</i> rhizome is lacking. Drying is regarded as the simplest and most cost-effective method for maintaining the integrity of bio-active substances in raw plant materials. Hence, in this study, we examined the impact of 24 different combination drying techniques, on the medicinally potential phytochemicals and antioxidant activities of <i>C. caesia</i> rhizome.</p> Methods <p><i>C. caesia</i> fresh rhizomes were collected from Khat Tettelia Namgaon, Kamrup metro District, Assam, India. Rhizomes were subjected to different drying treatments as described previously. Phytochemicals including phenol, flavonoid, saponin, and tannin contents were determined following standard methodologies. Antioxidant activity was determined by estimating IC₅₀ values of DPPH and ABTS radical scavenging assays.</p> Results <p>The results suggested that <i>C. caesia</i> rhizomes boiled at 80&#xa0;°C for 30&#xa0;min, followed by oven-drying at 70&#xa0;°C was the optimum drying condition for restoring phytochemicals like phenol (2.587&#xa0;mg GAE/g), flavonoid (20.238&#xa0;mg QE/g), tannin (5.4119 ± 0.1059&#xa0;mg TAE/g), saponin (16.06%) and maximum antioxidant activities with IC₅₀ values 6.571 ± 1.627&#xa0;mg/mL, and 1.878 ± 0.068&#xa0;mg/mL for scavenging DPPH and ABTS, respectively.</p> Conclusions <p>The findings of this study will be helpful for developing improved treatments for preserving and restoring active components of <i>C. caesia</i>.</p>