Background: hypothyroidism is of concern in our society; it has an effect on metabolic parameters. Objective: this study aimed to predict the prevalence of metabolic syndrome (MetS) among patients with hypothyroidism in Jeddah, Saudi Arabia and to determine the effect of treating hypothyroidism on MetS. Methods: we conducted this cross-sectional study, in which MetS was defined by presence of at least three of the five AHA/NHLBI criteria. We included patients with hypothyroidism that were managed in an outpatient department or admitted in King Abdulaziz University Hospital from 1 March to 30 April 2016. We measured lipid parameters, blood pressure (BP), waist circumference (WC) and serum fasting blood glucose (FBG). Results: in total 57 patients were included in our study, of which 47 (82%) were females. the majority of patients were greater than 50 years of age (n=35, 60%). We found that 36.8% of patients uncontrolled for hypothyroidism had high levels of TSH (serum level of TSH >5 mlu/L) , while 64.9% of patients who were controlled for hypothyroidism had normal levels of TSH (serum level of TSH 0.5 - 5 mlu/L). Overall, 71.9% (n=41) of hypothyroidism patients had MetS. However, we found that 51.8% (n=21) uncontrolled hypothyroidism patients suffered from MetS and 48.2% (n= 20) patients controlled for hypothyroidism suffered from MetS. However, 70.68 %, 31.03%, 34.48%, 79.31% and 70.6% of participants had abnormal waist circumference (WC), hypertriglyceridemia, abnormal high-density lipoprotein (HDL), hypertension and elevated serum levels of fasting blood sugar, respectively Conclusion: hypothyroidism plays an important role in MetS. Future advanced studies including larger numbers of patients are needed to test the effect of treating hypothyroidism on MetS. Routine screening for cardiovascular risk factors in patients with hypothyroidism may unmask MetS.