Nanotechnologies for intracellular delivery are of great value in clinical and biological research. Diamond nanoneedle arrays are a novel and attractive platform to facilitate drug delivery with minimal cytotoxicity. Using our technique, the cellular membranes can be temporarily disrupted for enhanced diffusion of drug molecules to cytoplasm. Herein we show that this technique is applicable to deliver different types of anticancer drugs into a variety of cell lines, although the membrane of each cell line possesses varied rigidity and hardness and each drug has its own unique properties and targets. When anticancer drugs and nanoneedle arrays are collaboratively used to treat cancer cells, the cell viability dramatically decreases by up to 40 % in comparison with the cells treated with drugs only. Attractively, therapeutic molecules can be efficiently delivered to drug-resistant cells with the aid of nanoneedle arrays. The combination of diamond nanoneedle arrays and anticancer drug cisplatin can decrease the viability of A549 cisplatin-resistant cells to about 60 %, while the cells only treated with the same concentration of drug are essentially not affected due to their drug resistance. These results indicate that dense nanoneedle arrays represent an effective approach to enhance the delivery of biological molecules to different types of cells. Such approach will certainly be beneficial to microbiological research and clinical applications in the future.