Background & Aims Familial adenomatous polyposis (FAP) is an inherited form of colorectal cancer (CRC) characterized by hundreds of adenomatous polyps in the colon and rectum. FAP is also associated with thyroid cancer (TC), but the lifetime risk is still unclear. This study reports the standardized incidence ratio of TC in Hispanic FAP patients. Methods TC incidence rates in patients with FAP were compared with the general population through direct database linkage from the Puerto Rico Central Cancer Registry (PRCCR) and the Puerto Rico Familial Colorectal Cancer Registry (PURIFICAR) between the periods of January 1, 2006 to December 31, 2013. The study population consisted of 51 Hispanic patients with FAP and 3,239 with TC from the general population. The Standardized incidence ratio (SIR) was calculated using the Indirect Method, defined as observed TC incidence among patients with FAP in PURIFICAR’s cohort (2006–2013) divided by the expected TC incidence based on the PR population rates (2006–2010). SIR values were estimated by sex (male, female and overall). This study received IRB approval (protocol # A2210207). Results In Hispanic patients with FAP the standardized incidence ratio (SIR) (95% CI) for TC was 251.73 (51.91 – 735.65), with higher risk for females 461.18 (55.85–1665.94) than males 131.91 (3.34–734.95). Conclusions Hispanic FAP patients are at a high risk for TC compared to the general population. Our incidence rates (SIR) are higher than previous studies, suggesting that this community may be at a higher risk for TC than previously assumed. Implementation of clinical surveillance guidelines and regular ultrasound neck screening in Hispanic FAP patients is recommended.