Variation in the production of defensive chemicals by seaweeds is an important feature to understand the ecological and evolutionary aspects of the predator-prey interactions in marine systems. In this study, we evaluated the inter- and intrapopulation variations in the amount of elatol, which is a sesquiterpene produced as a chemical defence in specimens from four populations of the red seaweed Laurencia dendroidea along the Brazilian coast. The concentration of elatol varied from 2 to 10 times among the L. dendroidea individuals but was approximately three orders of magnitude broader among the populations from 0.001% to 1.24% of the dry weight. The specimens collected at lower latitudes produced low amounts of defences, which did not support the hypothesis that chemical defences increase with a decrease in latitude. When cultivated under distinct temperatures, L. dendroidea specimens produced more defences (= elatol) under high temperatures (25°C). Although we observed a genotypic relevance for chemical defence, the environmental differences along the Brazilian coast support the hypothesis that the variability observed in elatol production by L. dendroidea was most likely influenced by small-scale changes in environmental factors.