Doxorubicin (DOX) is a widely used antineoplastic agent for a variety of carcinomas. However, it is cardiotoxic and leads to cardiomyopathy. Previous studies have indicated that omega-3 polyunsaturated acids (ω-3 PUFAs) have therapeutic effects on dilated and diabetic cardiomyopathies. However, whether ω-3 PUFAs exert therapeutic effects on DOX-induced cardiomyopathy remains unclear. In this study, we explored the effect and underlying mechanisms of docosahexaenoic acid (DHA), an important type of ω-3 PUFA, on DOX-induced cardiotoxicity and inflammation. H9C2 cardiac cells were exposed to DOX (5 μM) and interfered with by DHA (10 μM) for 4 hours. The effect of DHA on H9C2 cell viability was measured by Cell Counting Kit-8 assay. The levels of mRNA and protein expression of inflammatory cytokines were determined by real-time polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Reactive oxygen species and nitric oxide (NO) levels were determined by corresponding kits. The protein expression of key molecules in the nuclear factor-kappa B/inducible isoform of nitric oxide synthase/nitric oxide (NF-κB/iNOS/NO) signaling pathway was determined by western blotting. DOX-induced significant cytotoxicity and reactive oxygen species production in H9C2 cardiac cells. It also induced cardiac inflammation as evidenced by significantly increased expressions of inflammatory cytokines, including tumor necrosis factor-α, interleukin-6, interleukin-1β, monocyte chemoattractant protein-1, and inducible isoform of NO synthase. However, DHA effectively attenuated DOX-induced cytotoxicity and inflammation. A further mechanistic study revealed that DHA suppressed DOX-induced activation of the NF-κB/iNOS/NO signaling pathway in H9C2 cells. Our results indicate that DHA may protect against DOX-induced cardiotoxicity by inhibiting NF-κB/iNOS/NO signaling pathway activation.