The park is not a single continuous wilderness but a collection of three distinct zones. To the west of Kainji Lake lies the Borgu Game Reserve, covering more than 3,929 square kilometers of savanna woodland. Southeast of the lake, the Zugurma Game Reserve adds another 1,370 square kilometers. Between them, a protected section of the reservoir itself connects the terrestrial habitats with aquatic ones. The merger of Borgu and Zugurma in 1978 created a park large enough to support wide-ranging species like elephants and lions. Since 2005, Kainji has been designated a Lion Conservation Unit alongside Yankari National Park, an acknowledgment that these two reserves represent some of the last viable lion habitat in the region.

The park's fauna reads like an inventory of West African wildlife that has been squeezed out of most of its former range. Elephants, buffalo, roan antelope, and hartebeest move through grasslands broken by gallery forest along the rivers. Baboons and patas monkeys occupy the woodland edges. Nile crocodiles patrol the waterways, and clawless otters fish the quieter tributaries. Approximately 350 bird species have been recorded, from the imposing secretary bird and ground hornbill to smaller species like oriole warblers and bee-eaters. Great white pelicans work the lake margins, and rare pale arctic migrants pass through seasonally. The park is managed by the Federal National Park Service, which gives rangers the authority to pursue poaching cases under national park law rather than through local courts, a legal distinction that matters in a region where bushmeat hunting remains a persistent pressure.

The terrain undulates between rounded inselbergs, isolated rock formations that rise above broad pediments of eroded laterite. Rivers including the Oli, Menei, Doro, and Manyara carve channels that slope toward the Niger River valley, feeding the park's scattered waterfalls and seasonal pools. The climate swings between distinct wet and dry seasons: rains arrive in April and persist through November, delivering 1,100 to 1,200 millimeters annually. Temperatures range from cool mornings around ten degrees Celsius during the harmattan to regular highs near thirty degrees. The park opens to visitors from December through June, when the dry season makes roads passable and animals concentrate near remaining water sources.

Kainji Lake, the man-made reservoir that forms the park's eastern boundary, stretches 136 kilometers and hides a piece of history beneath its surface. The town of Old Bussa once stood here, notable as the place where the Scottish explorer Mungo Park met his end in 1806 during his second expedition to trace the Niger River to the sea. When the Kainji Dam was completed in 1968, the rising waters swallowed Old Bussa entirely. New Bussa was built to replace it, but the original town and whatever physical traces of Park's final journey it contained now lie at the bottom of the reservoir. Visitors can arrange boat tours of the lake through the Borgu Game Reserve office at Wawa, and fishing is permitted with authorization from the Nigeria Electric Power Authority.