Local vegetation varies from Cape Fynbos to Knysna-Amatole montane forests further inland.

Plettenberg Bay hosts one of the largest seagull breeding colonies along the South African coast at the mouth of the Keurbooms River, named after the indigenous keurboom tree. There are many pelagic birds in the area as well as the endangered African Oystercatcher which live along the shores.

The Robberg Peninsula is home to a large Cape fur seal colony, seals can often be seen in the surf off Robberg Beach. Great White Sharks, attracted by the seal colony, can also be spotted from the high ground of Robberg Peninsula. Southern Right whales are a common sight in the bay during their breeding season from July to December. Bryde's whales frequent the bay throughout the year being the most sighted during the summer months. Humpback whales migrate past during July and December. Killer whales (Orca) and Sei whales are occasionally sighted. Whales can be viewed from various viewpoints in the town as well as from Robberg Peninsula. Plettenberg Bay also boasts 3 species of dolphins which visit the bay throughout the year, these being the Bottlenosed dolphin, the Common dolphin and the endangered Humpback dolphin.

A distinctive flower-shaped sea shell called a pansy shell is endemic to this part of the coast, and is used as the symbol representing the town. Looking for these shells on the beach at low tide is a popular activity amongst visitors and locals alike. Robberg Peninsula is maintained as a nature reserve, allowing visitors to see many of the area's local plants and animals.

In December 1977, the area was impacted by an oil spill from the Venpet-Venoil collision, which occurred 60 km offshore when two supertankers collided.