Human disturbance to wildlife is on the rise and disturbance management is a key activity in conservation. Although disturbance can be controlled with relative ease in nature reserves that are properly resourced and managed by employed staff, most reserves do not fall into this category, and most wildlife exists outside managed reserves entirely. Thus, developing and demonstrating the effectiveness of simple, low-cost approaches to minimising disturbance is an important objective in conservation. In this study we examine the effectiveness of regulatory signs in controlling the behaviour and impacts of visitors on a colonial island-nesting bird, the Northern gannet (Morus bassanus), on an unmanaged island. First, we found that the percentage of successful nests declined with proximity to the disturbed edge of the colony, and was much higher in an undisturbed control area. Second, the number of birds displaced by visitors correlated negatively with the minimum visitor approach distance. Third, visitor proximity to the colony was dramatically reduced in the presence of a regulatory sign in comparison to periods without signs, which resulted in fewer birds being displaced from their nests. Photographers were the only visitor group who didn't always comply with the sign. Our results show that breeding success in a species often thought to be well adapted to human presence, suffers from tourist pressure, and that simple and informative regulatory signs can be a cost-effective way of reducing the disturbance caused by visitors at unmanaged wildlife sites.