microRNAs (miRNAs) are short non-coding RNA molecules, which post-transcriptionally regulate genes expression and play crucial roles in diverse biological processes, such as development, differentiation, apoptosis, and proliferation. Here, we investigated the possible role of miRNAs in the development of drug resistance in human lung cancer cell line. We found that miR-135a/b were downregulated while MCL1 was upregulated in A549/CDDP (cisplatin) cells, compared with the parental A549 cells. In vitro drug sensitivity assay demonstrated that overexpression of miR-135a/b sensitized A549/CDDP cells to cisplatin. The luciferase activity of MCL1 3'-untranslated region-based reporter constructed in A549/CDDP cells suggested that MCL1 was the direct target gene of miR-135a/b. Enforced miR-135a/b expression reduced MCL1 protein level and sensitized A549/CDDP cells to CDDP-induced apoptosis. Taken together, our findings first suggested that hsa-miR-135a/b could play a role in the development of CDDP resistance in lung cancer cell line at least in part by modulation of apoptosis via targeting MCL1.