Microfitolites (oncolites and catagraphites) are very widespread in the Neoproterozoic deposits of the south-east of the Siberian platform. Their biochemogenic (vegetable-lithogenic) nature remained insufficiently proven by factual material. However, many experts have used them as paleobiological objects in order to prove the age of deposits. In the sedimentary carbonate rocks of the Neoproterozoic of the middle course of the Lena river, and microfitolites are suitable for identifying their nature. Many of them, for example, named "osadia tenuilamellata" are similar to oolites and other carbonate grains of chemogenic origin, and it is often difficult to distinguish them without detailed studies of nature. In oncolites and catagraphites of the Neoproterozoic of the middle course of the Lena river, insections of the Kalanchevskaya, Chenchinskaya and Tinnovskya formations exposed near the Urinsk uplift, spherical and thread-like microorganisms are found, which presumably are photosynthetic cyanobacteria. They are represented by calcified cells and thread-like forms, and for the first time point to biochemogenic nature of microfitolites of the Neoproterozoic, but not chemogenic, as is customary in some publications. The obtained results can be used to clarify the facies conditions of sedimentation, which in the Pre-Patom trough are associated with the prediction of potential carbonate reservoirs (intermediate sources) of oil and gas in the section of the Neoproterozoic.