The Rio Cajari flows through the state of Amapá in northern Brazil, primarily within the protected area known as the Rio Cajari Extractive Reserve. This reserve encompasses a landscape of dense Amazonian rainforest and cerrado fields, creating a remote and natural setting for paddling. The waterway is central to the reserve's history, which is tied to the rubber extraction cycle that began in the mid-20th century. The overall character of a paddling trip here is one of immersion in a protected, biodiverse forest environment, with the river serving as a vital transportation and resource-gathering corridor for local extractivist communities.

Access to the river and the reserve is facilitated by Federal Highway BR-156, an unpaved road that crosses the northwestern portion of the protected area. This highway provides the primary access points for reaching the river. The best time to visit for paddling and travel is during the drier season, when paths and waterways are more navigable. Within the reserve, notable sights include the traditional Brazil nut groves, which are managed by local families who may spend weeks in the forest during the harvest. Paddlers should be aware that this is a working extractive reserve, and they will be sharing the environment with residents engaged in sustainable harvesting activities. The river's course through the reserve offers opportunities for multi-day trips, with the potential to observe the rich flora and fauna of the Amazon rainforest and cerrado transition zones.