The peninsula is steep and hilly, and is largely covered in subtropical rain forest.
The Coromandel Range forms a spine for the peninsula rising to nearly 900 metres, and the large island of Great Barrier, which lies beyond the northern tip, can be thought of as an extension of the range. Great Barrier is separated from Cape Colville on the peninsula's northern coast by the Colville Channel.
The towns are connected by State Highways 25 and 25A which form a circuit around the peninsula. At the base of the peninsula, the towns of Paeroa and Waihi are connected by means of a road through the Karangahake Gorge which separates the Coromandel Range from the Kaimai Ranges. Not all of the roads within the peninsula are sealed with tarmacadam, notably the 309 Road which connects Coromandel Town and Whitianga. Some hire car companies have contracts that specifically exclude driving on these roads.
Although the peninsula is close to large centres of population such as Auckland to the west and Tauranga to the southeast, its rugged nature means that much of it is relatively isolated, and the interior and northern tip are both largely undeveloped and sparsely inhabited. A forest park covers much of the peninsula's interior.
Numerous small islands and island groups lie offshore, such as the Motukawao Islands to the northwest, the Alderman Islands and Slipper Island to the southeast, and the Mercury Islands to the northeast.
The peninsula shows considerable signs of previous vulcanism. It comprises the eroded remnants of the Coromandel Volcanic Zone, which was active during the Miocene and Pliocene. Volcanic activity has since shifted southeast to the Taupo Volcanic Zone. The peninsula is also close to the Auckland Volcanic Field, which exhibits a very different style of vulcanism. Geothermal activity is still present on the Peninsula, with hot springs in several places, notably at Hot Water Beach, in the central east coast between Whitianga and Tairua.