In 1673 Dampier enlisted as a seaman in the Royal Prince, commanded by the famous Sir Edward Spragge, and fought in the Dutch war.

A year later he sailed to Jamaica in the Content, to take up a post as manager of a plantation belonging to a Colonel Hellier. His restless spirit soon revolted against this humdrum life on a plantation, and Dampier again went to sea, sailing in a small trading vessel amongst the islands.

Dampier's first step towards buccaneering was taken when he shipped himself on a small ketch which was sailing from Port Royal to load logwood at the Bay of Campeachy. This was an illegal business, as the Spanish Government claimed the ownership of all that coast, and did their best to prevent the trade. Dampier found some 250 Englishmen engaged in cutting the wood, which they exchanged for rum. Most of these men were buccaneers or privateers, who made a living in this way when out of a job afloat. When a ship came into the coast, these men would think nothing of coming aboard and spending thirty and forty pounds on rum and punch at a single drinking bout.

Dampier returned afterwards to take up logwood cutting himself, but met with little success, and went off to Beef Island. He had by this time begun to take down notes of all that appeared to him of interest, particularly objects of natural history. For example, he described, in his own quaint style, an animal he found in this island.

"The Squash is a four-footed Beast, bigger than a Cat. Its Head is much like a Foxes, with short Ears and a long Nose. It has pretty short Legs and sharp Claws, by which it will run up trees like a Cat. The flesh is good, sweet, wholesome Meat. We commonly skin and roast it; and then we call it pig; and I think it eats as well. It feeds on nothing but good Fruit; therefore we find them most among the Sapadillo-Trees. This Creature never rambles very far, and being taken young, will become as tame as a Dog, and be as roguish as a Monkey."

Dampier's first act of actual piracy was when he joined in an attack on the Spanish fort of Alvarado, but although the fort was taken, the townspeople had time to escape with all their valuables before the pirates could reach them. Returning to England in 1678, he did not remain long at home, for in the beginning of 1679 he sailed for Jamaica in a vessel named the Loyal Merchant. Shortly after reaching the West Indies, he chanced to meet with several well-known buccaneers, including Captains Coxon, Sawkins, and Sharp. Joining with these, he sailed on March 25th, 1679, for the Province of Darien, "to pillage and plunder these parts." Dampier says strangely little about his adventures for the next two years, but a full description of them is given by Ringrose in his "Dangerous Voyage and Bold Adventures of Captain Sharp and Others in the South Sea," published as an addition to the "History of the Buccaneers of America" in 1684.

This narrative tells how the buccaneers crossed the isthmus and attacked and defeated the Spanish Fleet off Panama City. After the death of their leader, Sawkins, the party split up, and Dampier followed Captain Sharp on his "dangerous and bold voyage" in May, 1680.

In April, 1681, after various adventures up and down the coast of Peru and Chile, further quarrels arose amongst the buccaneers, and a party of malcontents, of which number Dampier was one, went off on their own account in a launch and two canoes from the Island of Plate, made famous by Drake, and landed on the mainland near Cape San Lorenzo. The march across the Isthmus of Darien has been amusingly recounted by the surgeon of the party, Lionel Wafer, in his book entitled "A New Voyage and Description of the Isthmus of America," published in London in 1699.