To figure out plasma homocysteine (Hcy) status in patients with subclinical hypothyroidism (SH) and overt hypothyroidism (OH) compared with healthy subjects, and the effect of levothyroxine (L-T4) on plasma homocysteine status in patients with hypothyroidism. PubMed Web of Science, and The Cochrane Library were used to identify eligible studies. The Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of selected studies. All analyses were performed using the STATA, version 12 software. Our meta-analysis indicated that plasma Hcy concentrations elevated in OH patients without L-T4 treatment compared with healthy subjects. However, this elevation was not observed in the comparison between patients withSH without L-T4 treatment and healthy subjects. Moreover, plasma Hcy levels were found to be higher in patients with OH without L-T4 treatment than in patients with SH without L-T4 treatment. Finally, plasma Hcy concentrations decreased after L-T4 treatment in patients with SH or OH. Plasma Hcy status is associated with the severity of hypothyroidism and L-T4 treatment is helpful for patients with hypothyroidism to reduce the plasma Hcy levels.