Background/Objectives: ADCs bring an innovative strategy to cancer treatment by conjugating powerful cytotoxic agents to the specificity of monoclonal antibodies. This review discusses recent advancements and challenges in the field of ADCs, along with future potential applications. Methods: Studies focused on the development of ADCs were reviewed. These include the effects of payload improvements, linker technologies, antibody engineering, and ADC internalization, which were particular topics of examination regarding their role in pancreatic ductal adenocarcinoma (PDAC) and triple-negative breast cancer (TNBC). The efficacy of some ADCs for pancreatic and breast cancers was compared. Results: In TNBC, ADCs such as sacituzumab govitecan and trastuzumab deruxtecan have improved progression-free survival in advanced cases. In contrast, PDAC ADC development is challenged by low antigen density and poor internalization; despite evidence of target engagement in early trials targeting mesothelin and MUC1, ADCs for PDAC have yet to achieve significant clinical efficacy or regulatory approval. Conclusions: While ADCs have significantly advanced treatment options in TNBC, PDAC remains a difficult target due to its stroma-rich microenvironment and lack of high-density, tumor-specific antigens. This article emphasizes the need for tailor-made ADC designs to enhance results in various types of cancers and provides valuable insight into future advancements in precision oncology.