Systemic lupus erythematosus (SLE) is a systemic autoimmune disease that affects women of childbearing years. Pregnancy with SLE is associated with an increase risk of adverse maternal and fetal outcomes. Recently, tacrolimus has been used for steroid-resistant SLE. However, because of limited information regarding the use of immunosuppressants during pregnancy, many SLE patients give up pregnancy. We report two SLE patients receiving tacrolimus who hoped to become pregnant. Patient 1 was a 31-year-old woman diagnosed with SLE 6 years earlier and treated with tacrolimus for 3 years because her symptoms were not controlled with other immunosuppressants. Patient 2 was a 28-year-old woman diagnosed with SLE 13 years earlier and treated with tacrolimus for 3 years because her symptoms were not controlled with prednisolone alone. The medical ethics board in our hospital approved the use of tacrolimus during pregnancy and lactation, and informed consent was obtained from the patients. Both patients were well controlled during pregnancy with prednisolone (Patient 1: 12 mg/day and Patient 2: 10 mg/day) and tacrolimus therapy (3 mg/day). They had healthy newborns and continued breastfeeding with tacrolimus therapy. The blood concentrations of tacrolimus 12 hours after taking tacrolimus was 3.0 ng/ml in Patient 1 and 2.9 ng/ml in Patient 2, and their newborns' blood concentrations of tacrolimus 1 hour after breastfeeding were 0.2 ng/ml and 0.5 ng/ml, respectively. Both newborns are healthy for at least 3 years after birth. This is the first report on the safety of tacrolimus for pregnancy and lactation in patients with SLE.