Aim This study aimed to assess the relationship between loneliness and hypothyroidism in patients with hypothyroidism and to determine predictors of loneliness. Materials and methods A cross-sectional study was conducted on hypothyroid patients attending the endocrine clinics at Alhada Military Hospital and Prince Mansour Military Hospital, Taif, Saudi Arabia between the period of December 2020 and May 2021. Patients with more than 18 years of hypothyroidism were included and those with other thyroid diseases were excluded as well as those with other comorbidities and psychiatric disorders and those who were living alone. Data were collected using an online pre-structured questionnaire. Results The study included 231 hypothyroid patients with a mean age of 43.34 ± 12.9 years, and 90.9% were females. The majority (96.5%) were taking levothyroxine, and 27.3% were practicing physical activity. Only 2.2% of the participants had a high degree of loneliness, whereas 47.2%, 34.6%, and 16% had low, moderate, and moderately high degrees of loneliness, respectively. Discussion In this study, 2.2% of sampled hypothyroid patients had high (2.2%) or moderately high degrees of loneliness feelings (16%). Duration of hypothyroidism was a significant predictor for high loneliness score.