Nanoparticles have undergone extensive investigation as carriers for delivering drugs to cancer cells. Nevertheless, their limited specificity can be significantly improved by incorporating targeting ligands like aptamers. Aptamers have become an extensively investigated area in the realm of targeting applications and cancer therapy. Their three-dimensional configuration grants them precise targeting capabilities. Aptamers exhibit targeting characteristics at a significantly lower cost than antibodies, owing to their DNA/RNA composition and straightforward chemical synthesis. They possess greater stability and have a small size that enhances their efficiency for transportation purposes. Combining nanoparticles with aptamers presents a fascinating approach to precise administration, treatment, and detection of cancer. Numerous aptamers have been created and examined specifically to combat cancer. In the following chapter, some of the most studied aptamers are described, followed by a section elaborating on the use of aptamer-based nanoparticles for the treatment and diagnosis of ovarian cancer, breast cancer, prostate cancer, leukemia, and lung and gastric cancer.