Although microseismic monitoring of hydraulic fractures has primarily been concerned with the dimensions, complexity, and growth of fractures or fracture systems, there is an ever-increasing desire to extract more information about the hydraulic-fracturing and/or natural fractures from microseismic data. Source mechanism analysis, which is concerned with deducing details of the failure process from the microseismic waveform data, is, therefore, attracting more attention. However, most of the studies focus more on the moment-tensor inversion than on extracting fault-plane solutions (FPSs) from inverted moment tensors. The FPSs can be extracted from the inverted moment-tensor, but there remains a question regarding how errors associated with the inversion of the moment-tensor affect the accuracy of the FPSs. We examine the uncertainties of FPS, given the uncertainties of the amplitude data, by looking into the uncertainty propagation from amplitude data into the moment-tensor and then into the resultant FPS. The uncertainty propagation method will be demonstrated using two synthetic examples.