Abstract: Objectives: NOS1AP is an adaptor protein of neuronal nitric oxide synthase 1. It plays an important role in the regulation of cell proliferation and apoptosis, as well as in the development of neuronal dendrites and other processes. A number of studies suggest an association between NOS1AP aggregates and mental disorders such as schizophrenia. In our laboratory, it was shown that NOS1AP aggregates is capable of aggregation in mammalian cells when overproduced. Previously, the amyloidogenic properties of NOS1AP aggregates isolated from human HEK293T cells had not been thoroughly examined. Methods: In this work, the immunoprecipitation method was optimized for NOS1AP aggregate isolation from HEK293T cells by determining the suitable concentration of polyclonal NOS1AP antibodies. Samples obtained as a result of immunoprecipitation were examined for the presence of amyloid properties by Congo red staining. Results and Discussion: The isolated NOS1AP aggregates, stained with Congo red, did not demonstrate apple-green birefringence in polarized light and had an amorphous, rather than fibrillar, morphology. Conclusions: The results obtained provide evidence supporting the non-amyloid nature of NOS1AP aggregates in human cells.