Curcuminoids are bioactive polyphenolics with potent antiinflammatory properties. Although several lines of in vitro and preclinical evidence suggest potent anticancer effects of curcuminoids, clinical findings have not been conclusive. The present randomized double-blind placebo-controlled trial aimed to evaluate the efficacy of curcuminoids as adjuvant therapy in cancer patients. Eighty subjects with solid tumors who were under standard chemotherapy regimens were randomly assigned to a bioavailability-boosted curcuminoids preparation (180 mg/day; n = 40) or matched placebo (n = 40) for a period of 8 weeks. Efficacy measures were changes in the health-related quality of life (QoL) score (evaluated using the University of Washington index) and serum levels of a panel of mediators implicated in systemic inflammation including interleukins 6 (IL-6) and 8 (IL-8), TNF-α, transforming growth factor-β (TGFβ), high-sensitivity C-reactive protein (hs-CRP), calcitonin gene-related peptide (CGRP), substance P and monocyte chemotactic protein-1 (MCP-1). Curcuminoid supplementation was associated with a significantly greater improvement in QoL compared with placebo (p < 0.001). Consistently, the magnitude of reductions in TNF-α (p < 0.001), TGFβ (p < 0.001), IL-6 (p = 0.061), substance P (p = 0.005), hs-CRP (p < 0.001), CGRP (p < 0.001) and MCP-1 (p < 0.001) were all significantly greater in the curcuminoids versus placebo group. In contrast, the extent of reduction in serum IL-8 was significantly greater with placebo versus curcuminoids (p = 0.012). Quality of life variations were associated with changes in serum TGFβ levels in both correlation and regression analyses. Adjuvant therapy with a bioavailable curcuminoid preparation can significantly improve QoL and suppress systemic inflammation in patients with solid tumors who are under treatment with standard chemotherapy protocols. Copyright © 2014 John Wiley & Sons, Ltd.