This study aimed to investigate the effects of curcumin (Cur) on the proliferation, migration, and invasion of gemcitabine (GEM) resistant lung cancer A549 cells (A549/GEM), and the potential mechanism. After treating with GEM, individually or combined with Cur, the inhibition, migration, and invasion of A549/GEM were tested by the CCK8, transwell, and cell wound healing assays, respectively. QRT-PCR and Western blot were used to detect mRNA and protein markers. Finally, the therapeutic effects of GEM, individually or combined with Cur, were verified in nude mice. The results indicated that the combined application of Cur and GEM can improve the sensitivity of A549/GEM to the GEM. Compared with the GEM, GEM plus Cur significantly decreased the migration and invasion of A549/GEM cells. The expression levels of MMP9 , Vimentin, and N-cadherin were significantly decreased, while the E-cadherin expression was increased. In vivo experiments showed a better therapeutic effect of GEM combined with Cur than that of GEM alone, and the combination therapy did not cause more toxicity to animals. In summary, Cur reversed GEM resistance and inhibited the EMT process in A549/GEM cells. GEM, combined with Cur, is safe and more effective in the treatment of non-small cell lung cancer.