This research explores the dynamics of urban informality and space appropriation at pedestrian bridges in Islamabad, Pakistan, offering new insights into how informal practices reshape the utilization and value of urban spaces. By focusing on both formal and informal uses, the study reveals a significant gap between the intended and actual uses of these bridges. Through observation and analysis of three key bridges, the study examines how informal activities–such as vending, resting, and social interactions–transform pedestrian bridges into multifunctional spaces. This research also uncovers informal modifications and analyzes the role of urban governance in shaping these practices. The findings contribute novel insights into urban informality in the Global South by focusing on Islamabad’s pedestrian bridges, an area that has received limited scholarly attention. The study is particularly valuable for urban planners and policymakers in guiding the design of more inclusive urban environments in Islamabad, Pakistan.