To compare the therapeutic effect between autologous serum and umbilical cord serum eye drops in the treatment of severe dry eye syndrome. Prospective case-control study. Ninety-two eyes of 48 patients with severe dry eye syndrome (34 eyes of 17 patients with Sjögren syndrome and 58 eyes of 31 patients with non-Sjögren syndrome) were treated with either 20% autologous serum (41 eyes of 21 patients) or umbilical cord serum eye drops (51 eyes of 27 patients). Symptom scoring, corneal sensitivity test, tear film break-up time (BUT), Schirmer test, tear clearance rate (TCR), corneal fluorescein staining, and conjunctival impression cytologic analysis were performed before and one month and two months after treatment. Both autologous serum and umbilical serum treatments led to improvement in the symptom score, tear film BUT, keratoepitheliopathy score, and impression cytologic findings. Symptom and keratoepitheliopathy scores were lower at one month (P = .03 and P = .12) and two months (P = .04 and .02) for those treated with umbilical cord serum compared with those treated with autologous serum. In Sjögren syndrome patients, goblet cell density was higher at two months of umbilical cord serum treatment compared with autologous serum treatment (P = .04). Umbilical cord serum eye drops were more effective in decreasing symptoms and keratoepitheliopathy in severe dry eye syndrome and increasing goblet cell density in Sjögren syndrome compared with autologous serum eye drops.