A novel catalyst-free synthetic strategy for producing high-quality CdTe nanowires in solution is proposed. A special reaction condition is intentionally constructed in the reaction system to induce the formation of nanowires through oriented in situ assembly of tiny particles. To establish such special synthetic conditions in the CdTe system, not only are its typical features and possible solutions deeply analyzed, but also related factors, such as the ligand environment, injection and growth temperature, and Cd-to-Te precursor ratio, are systemically investigated. High-quality ultralong (up to 10 μm) and ultrathin (less than 10 nm) CdTe nanowires are produced in solution under optimal reaction conditions. Morphological, spectral, and compositional analyses are performed to examine the products formed at different reaction stages in order to clarify the formation mechanism of the CdTe nanowires. Furthermore, the transformation of the CdTe nanowires into CdTe/CdSe core–shell heterostructures is intensively explored, and the CdSe epitaxial growth process is specially tracked by morphological and spectral characterization techniques. Finally, CdTe nanowires coated with a continuous and dense CdSe shell are successfully fabricated by using a proper coating protocol.