The best currency to take to St. Lucia is the Eastern Caribbean Dollar (XCD), often referred to as the "EC." While the US Dollar (USD) is widely accepted at major resorts, duty-free shops, and tourist restaurants, you will almost always receive a better high-value rate if you pay in the local currency. The EC is pegged to the US Dollar at a fixed rate of $1 USD = $2.70 XCD, but many local street vendors or small "rum shops" may only give you a rate of 2.50 if you pay in USD, effectively costing you a 10% "convenience tax." A high-value peer tip for 2026: bring some USD in small bills for tipping at the airport and hotel, but use an ATM on the island (like those at Bank of Saint Lucia) to withdraw EC for your daily excursions and local meals. This ensures you aren't "carrying a bank" and that you're getting the official interbank exchange rate, giving you the highest value for your Caribbean vacation budget.