Intermodular connections play an important role in the constructability and performance of modular building structures. The wind-generated vertical uplift force and the lateral load on modular structures raise concerns about the tensile and shear capacity of the intermodular connection joints. This study focuses on investigating the change in load response behaviour, working mechanism and performance of endplate-type intermodular connections with varying design parameters. Initially, the paper presents the design criteria of endplate-type intermodular connections and their behaviour, with a detailed theoretical approach, to identify their performance and capacity under tensile and shear loads. Then, the capacity of the proposed connections in this study was evaluated based on both the presented theoretical design and numerical approaches. The design inspiration for the proposed connection was taken from literature using which the finite element models for 4 specimens were developed and validated. The validated connection models were then used to conduct parametric studies for 11 proposed models, focused on changes in base endplate thickness (8 mm, 10 mm and 12 mm) and steel grade (s275 and s355), bolt hole diameter (22 mm, 26 mm and 30 mm) and tolerance, bolt grade (8.8, 10.9 and 12.9) and applied preload (0, 50 kN, 90 kN and 110 kN) with and without additional plate over oversized bolt holes. The results obtained from both shear and tensile performance analysis indicate that the change in proposed design parameters has a greater impact on shear over tensile behaviour and capacity. Further, the conducted parametric studies helped in identifying the optimum design parameter combinations for enhanced connection performance which are also cost-effective and ideal for an onsite installation. Finally, the paper suggests recommendations for future research and essential advancement in the endplate-type intermodular connection design in enhancing performance and presents the practical limitations and challenges in using such techniques.