*Purpose: In Croatia, the first case of coronavirus disease (COVID-19) has been reported on 25 February 2020; however, the COVID-19 seroprevalence in the liver (LTR) and kidney transplant recipients (KTR) is presently unknown.

*Methods: From 9 September to 13 November 2020, at the beginning of the second wave COVID-19 epidemic curve in Croatia, we performed a systematic screening for COVID-19 in outpatient solid organ transplant recipients (n=495). Serum samples were tested for the presence of SARS-CoV-2 IgG antibodies. Serological tests were performed by a commercial enzyme-linked immunosorbent assay (ELISA) using spike glycoprotein (S) and nucleocapsid protein (N) antigens (Vircell, Granada, Spain).

*Results: LTR (n=265) were older than KTR (n=230) (59.8±10.7 vs 51.8±12.1 years, p<0.01). Out of 495 transplant recipients, 97 (19.6%) were positive for anti-SARS-CoV-2-IgG. There was no difference in the seroprevalence between LTR and KTR, 20.4% vs. 18.7%, respectively, p>0.05. Anti-SARS-CoV-2-IgG were found in both symptomatic and asymptomatic patients. However, seropositive patients reported a significantly higher incidence of fever (25.3% vs. 12.8%, p=0.011) and anosmia (5.2% vs 0.9% p=0.023). Out of 97 anti-SARS-CoV-2-IgG positives, only 22% reported previous nasal-throat swabs RT-PCR testing, with 28.6% of them being SARS-CoV-2 RNA positive.

*Conclusions: In Croatia, the SARS-CoV-2 seroprevalence in LTR and KTR is 19.6% with seropositivity documented in both symptomatic and asymptomatic patients. The presence of specific symptoms increases the likelihood of SARS-CoV-2 seropositivity. The COVID-19 screening program should be increased in Croatia.

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