BACKGROUND: A wide array of products in the category of complementary or alternative medicine for cardiovascular disease and prevention are readily available on online retail platforms. However, a critical assessment of these products, including their therapeutic claims, has not been previously performed. METHODS: "Heart failure supplement" and similar terms were entered into the Amazon.com search engine, and all medication products including claims, content, and formulations were individually evaluated. RESULTS: We identified 111 products, most of which lacked safety information. They included, on average, 8.2 ingredients. The median cost per order was 7.60. The majority were in capsule form (58.6%), and the most common ingredient was coenzyme Q10. All included a legal disclaimer. Physician testimonials were included in only 3 product listings. CONCLUSIONS: Given the popularity of complementary and alternative medicine and their easy accessibility through online retailing, and the fact that prior studies suggest a minority of patients discuss use with their providers, further study is needed to evaluate the extent of and the potential for both undiagnosed drug-drug interactions and replacement of guideline-directed medical treatment for heart failure with unapproved products.