The rapid evolution of electric vehicle (EV) technology has intensified the demand for high-power density power converters capable of delivering superior efficiency, compactness, and reliability. As switching frequencies increase and wide bandgap semiconductor devices such as silicon carbide (SiC) and gallium nitride (GaN) are increasingly adopted, thermal management has emerged as a critical design constraint in next-generation EV converters. Excessive heat generation due to conduction and switching losses significantly affects junction temperature, conversion efficiency, packaging integrity, and long-term reliability. Conventional air-cooled and basic liquid-cooled systems are often insufficient to meet the thermal requirements of high-power density architectures. This study investigates the impact of advanced thermal management techniques on the performance, efficiency, and reliability of high-power density EV converters. A comparative evaluation is conducted among several state-of-the-art cooling strategies, including enhanced liquid cooling with integrated cold plates, microchannel heat sinks, two-phase cooling systems, jet impingement cooling, heat pipes, vapor chambers, and phase change materials (PCM). Electro-thermal modeling and computational fluid dynamics (CFD) simulations are employed to analyze heat distribution and thermal resistance under varying load and ambient conditions. Experimental validation is performed using a prototype high-frequency SiC-based DC-DC converter platform operating under dynamic driving profiles. Results demonstrate that advanced cooling techniques can reduce semiconductor junction temperatures by 20–45% compared to conventional liquid cooling systems, leading to measurable improvements in efficiency (1.5–3%), increased allowable switching frequency, and enhanced power density exceeding 30%. Two-phase and microchannel cooling methods exhibit superior heat flux removal capabilities, while passive solutions such as heat pipes and PCMs provide effective transient thermal buffering. Furthermore, thermal cycling analysis indicates a substantial improvement in predicted mean time to failure (MTTF), highlighting the direct relationship between thermal mitigation and converter reliability. The findings confirm that integrating advanced thermal management strategies is essential for enabling compact, high-efficiency, and durable EV power converters. The study provides quantitative performance comparisons and design guidelines that support the development of next-generation electric mobility power electronics systems.