The exosomes, nano-sized cup-shaped extracellular vesicles measuring 30–150 nm in size, have extended their potential use as a tumor biomarker in recent years. These exosomes are stated to be the carbon copy of the cells of origin, mirroring the exact physiological or pathological state of their parent cell, including cancer cells. Pertaining to cancer, it is generally believed “the sooner, the better.” Most of the currently available diagnostic techniques are not devoid of their side effects, in that they are invasive and hazardous. These conventional diagnostic tools are considered less beneficial as they only detect cancer in its later stages, leading to poor treatment efficiency. This is where the use of exosomes comes into play, as these are less invasive methods of diagnosis, secreted and released into circulation in the early stages of cancer, and are easily detectable. Accounting for the presence of cargo it carries, such as proteins, nucleic acids, lipids, and metabolites, exosomes have garnered considerable attention from the scientific community worldwide for their remarkable role as an efficient diagnostic tool. Among the various nucleic acids transported by exosomes, microRNAs (miRNAs) are a class of small, noncoding RNAs that have gained significant attention due to their critical role in posttranscriptional gene regulation via interaction with target mRNAs. Notably, under pathological conditions and cellular stress, cells tend to secrete higher levels of miRNAs into the extracellular environment, often encapsulated within exosomes. These circulating, exosome-associated miRNAs have emerged as promising noninvasive biomarkers for various diseases, particularly cancer. This chapter explores the biological characteristics of exosomal miRNAs, the molecular mechanisms that govern their selective packaging into the exosomal lumen, and their significant implications for early cancer detection. Special emphasis is placed on their diagnostic relevance and how their profiling may aid in enhancing the overall efficacy of cancer therapy.