<p>Inadequate planning and management of nature-based tourist activities can significantly affect marine environments, causing unintended negative impacts on marine environmental ecosystems. The Pacific islands, with their diverse marine ecosystems and tourism-dependent nature, provide a unique context for investigating the interaction between tourists and the marine environment. Despite this, few studies have examined how nature-based tourist activities affect the marine environment in the Pacific. This paper addresses this gap by conducting systematic reviews of existing literature to identify tourists’ impacts on the marine environment in the Pacific, with a particular focus on tourists’ behaviour and its determinants. It also explores the theories and practices used to support changes in tourists’ behaviour to mitigate adverse effects on the marine environment. The study highlights that pro-environmental research has traditionally relied on a limited set of theoretical frameworks, highlighting the need for more diverse approaches to effectively address the environmental challenges posed by tourist activities.</p>