Objectives: The study identified factors affecting anti‐S immunoglobulin G production after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) in kidney transplant recipients. Methods: Serum samples were prospectively collected from kidney transplant recipients, live kidney donors, and healthy volunteers 1 month after receiving the second dose of SARS‐CoV‐2 vaccine, and anti‐S immunoglobulin G titers were measured. The mycophenolate mofetil dose was reduced before vaccination in some immunologically low‐risk recipients. Results: A total of 151 kidney transplant recipients, 74 live kidney donors, and 50 healthy volunteers were included. Kidney transplant recipients had significantly lower titers of anti‐S immunoglobulin G than donors and healthy volunteers (1377 ± 246, 8310 ± 932, and 9908 ± 1040 AU/ml, respectively). Only 67.3% of kidney transplant recipients, compared to 100% of donors and healthy volunteers, were positive for anti‐S immunoglobulin G. Among the kidney transplant recipients, the anti‐S titer was higher in younger recipients, those with higher peripheral blood lymphocyte counts and glomerular filtration rates, those without a history of antithymocyte globulin use, and those who had discontinued or received a reduced dose of mycophenolate mofetil. Younger age, higher lymphocyte count, glomerular filtration rate, and mycophenolate reduction were significantly associated with anti‐S immunoglobulin G > 1000 AU/ml in nominal logistic regression analysis. There were no rejection episodes after mycophenolate modification in kidney transplant recipients. Conclusions: Anti‐S immunoglobulin G production after vaccination was attenuated in kidney transplant recipients. Mycophenolate mofetil cessation or reduction is a modifiable means to enhance anti‐S immunoglobulin G production in immunosuppressed kidney transplant recipients. [ABSTRACT FROM AUTHOR]