Seaweed consumption is increasing around the world due to consumer demands for sustainable food sources, health benefits derived from bioactive compounds, and a source of novel flavors. Despite all the benefits that come with eating seaweed, consumers still resent of their sensorial properties. Seaweed is traditionally consumed raw or cooked, but there is still not enough information on how the sensory descriptors and bioactive compounds change when cooked. The aim of this study was to determine the change in total polyphenol content (TPC), antioxidant capacity (e.g., DPPH and ORAC values) and changes in volatile compounds of three Chilean seaweeds: Durvillaea antarctica, Pyropia spp. and Ulva lactuca when subjected to traditional cooking for 15 min at 100°C. In all three seaweeds, TPC decreased with cooking and so did the measured antioxidant capacity. Altogether, 46 volatile cpmpounds were identified in D. antarctica, 49 in Pyropia spp. and 47 in U. lactuca. The concentration of these volatile compounds was correlated with aroma sensory descriptors of the same samples. Consumer preferences may be attracted by the herbal notes of U. lactuca or the sweet, caramel, and umami flavors of D. antarctica and Pyropia.