Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) elicits cellular and humoral immune responses. In patients with coronavirus disease 2019 (COVID-19), IgM, IgA, and IgG antibodies against SARS-CoV-2 emerge within a few days, 1 and can be detected in serum and oral fluids. 2 Although IgA and IgM antibodies vanish within about 2 months, IgG levels persist for at least 8 months in the general population. 3 SARS-CoV-2 seropositivity in patients on dialysis has been demonstrated, 4,5 but data on SARS-CoV-2 antibody dynamics are limited.Although repeated blood draws in patients on hemodialysis pose no major medical or logistic problems, the situation is different in patients on peritoneal dialysis (PD) who lack permanent vascular access. Therefore, we explored the presence or absence of SARS-CoV-2 antibodies in 96 spent PD dialysate samples from 58 patients as a complement for blood samples. Patients are classified into four groups: patients on chronic PD, prepandemic (Group 1; collected between May 2019 and February 2020); patients who were COVID-19 negative and on chronic PD (Group 2; collected between March and September 2020); patients with COVID-19 and on chronic PD (Group 3; collected between March and September 2020); and patients with Acute Kidney Injury (AKI), COVID-19, and treated with acute PD (Group 4; from April 2020). All patients in Group 3 and Group 4 were confirmed by SARS-CoV-2