To report on the incidence and use of kelp among patients with thyroid cancer. Data were collected using a web-based online anonymous survey under Institutional Review Board approval from Boston University. This report is based on 27 responses from subjects with thyroid cancer who use kelp. Demographic factors and complementary and alternative use were included. Respondents were primarily over age 40, white, female and have at least a high school education. The top five modalities were multivitamins, special diets, herbal supplements, prayer for health reasons and herbal tea. Only one patient reported perceiving a particular modality had a negative effect on treatment. Complementary and alternative medicine (CAM) was more often perceived as being used to aid their thyroid cancer treatment than to help with symptoms. On average, respondents who use kelp also use at least 11 additional CAM modalities. Only 1/2 of respondents who use kelp reported telling their physicians about their CAM use, and nearly 1/3 of respondents reported their CAM use was neither known, prescribed nor asked about by their physicians. In comparison to both national surveys of the general US population and patients with thyroid cancer, kelp users with thyroid cancer use at least twice the number of additional CAM therapies and report their use far less often. Physicians who treat patients with thyroid cancer should be aware of these data to further assist in their assessment and care.