The aim of the present study was to determine the effects of dietary lanthanum oxide levels (0, 100, 200, 300, or 400 mg/kg) on the laying performance, egg quality, fatty acids composition of yolk, egg lipid peroxidation, and some blood serum parameters of laying hen. One hundred twenty 22-wk-old brown Lohman LSL laying hens were randomly assigned to 5 groups with 6 replications. Dietary supplementation of 400 mg/kg lanthanum oxide significantly (P < 0.05) increased egg production. The addition of lanthanum oxide to the diet of laying hens' had no effect on feed intake and egg weight (P > 0.05). Supplementation of 100 and 200 mg/kg lanthanum oxide to diet caused a significant (P < 0.05) increase in Haugh unit and eggshell breaking strength. Blood parameters were not affected by supplementing lanthanum oxide. Malondialdehyde (MDA) concentration of serum decreased significantly (P < 0.05) with supplementation of 300 mg/kg lanthanum oxide to laying hen diets. It was also observed that thiobarbituric acid reactive substance (TBARS) values in egg yolk decreased significantly (P < 0.01) with supplementation of lanthanum oxide in diets. Supplementation of 100 mg/kg lanthanum oxide increased saturated fatty acid (SFA). In conclusion, dietary supplementation of lanthanum oxide had positive effects on feed conversion ratio, egg production, and egg shelf life. According to these results, it might be advised to supplement laying hens feed with lanthanum oxide as a feed additive.