In Nigeria's informal mobile phone accessory markets, products often fail prematurely yet consumer satisfaction remains surprisingly high, a paradox that is poorly understood in semi-urban northern contexts where formal consumer protection is weakest. This study therefore examines the combined and individual effects of perceived physical durability, informal warranty availability (7-day vendor guarantee), and visual similarity to original branded products on consumer satisfaction with mobile phone accessories across seven GSM markets in Katsina metropolis. Drawing on a cross-sectional survey of 412 consumers who had purchased accessories within the preceding six months, data were analysed using hierarchical multiple regression while controlling for age, income, and market location. Results show that perceived durability has the strongest positive effect on satisfaction (β = 0.41, p < 0.001), followed by warranty availability (β = 0.29, p < 0.001), and visual similarity (β = 0.16, p < 0.001), with the three factors jointly explaining 46.2% of variance in satisfaction (Adjusted R² = 0.455). Notably, only 37.9% of consumers received any informal warranty from vendors, indicating a market failure despite the substantial satisfaction gains associated with warranty provision. These findings demonstrate that consumers in informal markets prioritise functional durability over visual appearance, and that even low-cost verbal warranties can significantly enhance satisfaction by reducing perceived risk. We therefore recommend that vendors offer visible 7-day informal warranties and invest in demonstrable durability improvements, while regulators should consider mandating minimum warranty standards and launching targeted consumer education campaigns across Katsina's GSM markets, including Kofar Kaura, Sabonlayi, Green House, Kasuwar Tsaitsaye, Yar Kutungu, Continental Computers, and Sabuwar Unguwa.