Objectives: We sought to investigate the epidemiology of thyroid cancer and its trends in Oman over a 20-year period. Methods: We analyzed all cases of primary thyroid cancer reported to the Oman National Cancer Registry between 1996 and 2015. Agestandardized incidence rates (ASR) were calculated using the World Standard Population. Joinpoint regression was used to assess trends and obtain annual percentage changes (APC) in incidence rates with 95% confidence intervals (95% CI) and p-values at the alpha = 0.050 level. Gender-specific APC was used to project thyroid cancer incidence rates in Oman over the next 20 years. Population attributable fraction was calculated for obesity and current non-smoking. Results: A total of 1285 cases of primary thyroid cancer cases were registered in Oman between 1996 and 2015, with a female to male ratio of 4:1. In men, the ASR was 2.0 per 100 000 while in females it was 7.6 per 100 000 (p < 0.010). Over 80.0% of thyroid tumors were of a papillary type and 19.0% follicular type. Statistically significant trends for thyroid cancer were detected in women from 2008–2015 (APC = 14.3%, 95% CI: 8.0–20.9, p < 0.010) and among both genders (APC = 16.7%, 95% CI: 4.9–29.9, p < 0.010). If current trends continue, thyroid cancer incidence will increase to 3.1, 16.6, and 11.8 per 100 000 by 2040 in men, women, and both genders, respectively. Nearly 10.0% of thyroid cancer can be prevented by controlling obesity in the Omani population. Conclusions: Oman has had moderate incidence rates of thyroid cancer with an increasing trend among women. Since projections estimate that the rates of this disease will double in women over the next 20 years, health authorities should consider providing sufficient resources to manage this condition and establish prevention programs that address obesity as part of the strategy for the prevention and control of noncommunicable diseases.