Single agent therapy in the treatment of cancer did not provide satisfactory clinical outcome in a long term due to drug resistance, cumulative toxicity and suboptimal efficacy. Therefore, combination therapies are apt to improve the quality of life in patients. In the present study, combinatorial effect of EPA and/or DHA with doxorubicin (Dox) was evaluated for their potential synergistic effect on human lung adenocarcinoma (A549) cells. The respective IC50 values obtained for EPA, DHA and Dox were 170, 140 and 2.5 μmol/L and thus EPA and DHA were separately combined with Dox at constant ratio of 68:1 and 56:1 respectively, depending on the ratio of their IC50 values. Different combinations of drugs revealed dose-dependent inhibition of cell viability and IC50 values were reduced to nearly 3-fold (58.75 μmol/L) and 4.5-fold (31.5 μmol/L) in EPA-Dox and DHA-Dox combination respectively. Combination index (CI) revealed strong synergism (CI < 0.5) in DHA-Dox (0.49) and moderate synergism (CI > 0.5) in EPA-Dox (0.79) at 0.5 Fa (Fraction affected), which is further confirmed by dose reduction index and isobologram. The mechanisms underlying synergistic interactions involve intracellular ROS generation and MMP depolarisation which causes changes in the cell morphology viz. Nuclear fragmentation/condensation, membrane blebbing and early/late apoptotic cells. Moreover, cell cycle arrest was observed at the S and G2/M phase, with more prominent effect in G2/M phase. No toxicity was imposed on non-cancerous HEK-293 T cells. These findings suggest that EPA-Dox and DHA-Dox could be explored further for animal studies and clinical trials for lung adenocarcinoma treatment.