SARS-CoV-2 serological assays are urgently needed for rapid diagnosis, contact tracing and for epidemiological studies. So far, there is limited data on how commercially available tests perform with real patient samples and if positive tested samples show neutralizing abilities. Focusing on IgG antibodies, we demonstrate the performance of two ELISA assays (Euroimmun SARS-CoV-2 IgG and Vircell COVID-19 ELISA IgG) in comparison to one lateral flow assay ((LFA) FaStep COVID-19 IgG/IgM Rapid Test Device) and two in-house developed assays (immunofluorescence assay (IFA) and plaque reduction neutralization test (PRNT)). We tested follow up serum/plasma samples of individuals PCR-diagnosed with COVID-19. Most of the SARS-CoV-2 samples were from individuals with moderate to severe clinical course, who required an in-patient hospital stay. For all examined assays, the sensitivity ranged from 58.8 to 76.5% for the early phase of infection (days 5-9) and from 93.8 to 100% for the later period (days 10-18). With exception of one sample, all positive tested COVID-19 follow up-samples, using the commercially available assays examined (including the in-house developed IFA), demonstrated neutralizing properties in the PRNT. Regarding specificity, some samples of endemic coronavirus (HCoV-OC43, HCoV-229E) and Epstein Barr virus (EBV) infected individuals cross-reacted in the ELISA assays and IFA, in one case generating a false positive result. This article is protected by copyright. All rights reserved.