This study presents a comparative analysis of the seismic vulnerability and retrofit strategies for multi-residential buildings constructed in Slovenia during two distinct periods: the interwar period (1918–1941) and the early post-World War II period (1945–1963). These buildings, representative of the architectural heritage in the Balkan region, pose significant challenges in terms of seismic safety and cultural preservation. Building upon our previous research on post-war structures, we extend our investigation to include interwar buildings, allowing for a comprehensive comparison of construction techniques, materials, and seismic performance across these pivotal periods in Slovenian architectural history. The study employs a multi-faceted approach, combining historical research, architectural analysis, and advanced numerical modeling techniques. A typological classification system is developed for both periods, categorizing buildings based on their architectural and structural characteristics. Representative building types are then subjected to detailed seismic performance assessments using the equivalent frame approach with 3Muri software. The analysis reveals distinct vulnerabilities and strengths associated with each period’s construction practices. Based on these findings, we propose retrofit strategies that address the specific needs of each building type while respecting their historical and cultural significance. The strategies are evaluated for their effectiveness in improving seismic performance and their impact on the buildings’ architectural integrity. This research contributes to the broader understanding of the seismic risks faced by historical multi-residential buildings in the Balkan region and provides valuable insights for developing context-sensitive retrofit solutions. The findings have implications for both preservation efforts and seismic risk mitigation policies in Slovenia and the wider Balkan area.