Fluvial geomorphology, especially river terrace, is commonly used as the reference to constrain the magnitude, timing, rate, and spatiotemporal patterns of deformation of the underlying structure in the studies of neotectonics, tectonic geomorphology, and active tectonics. Based on many years of research work in the north piedmont of the Chinese Tianshan Mountains, it is found that there are some potential uncertainties of deformation rate deriving from fluvial geomorphology. ① The uncertainty related to the strategy dating terrace formation age. For young terraces (especially having an age of Latest Pleistocene—Holocene), the deformation rates constrained by the age of the top of terrace deposits and the basal age of the overlying loess could be significantly different from each other. The difference between the two rates for the Sangequan River terrace T2 in the northern Chinese Tianshan foreland is up to 50%. In contrast, for older terraces, the difference between the rates of deformation derived from the age of the top of terrace deposits and the basal age of the overlying loess could be negligible. ② The uncertainty related to terrace correlation among rivers. Along the strike of a structure, the response of river processes (such as sedimentation and terrace formation owing to river incision) to tectonic activation (bedrock uplift of the folds) is not synchronous. Therefore, for different rivers developed over the same anticline structure, using the age of a dated terrace of one river to determine the age of an undated terrace of another river based on terrace correlation between rivers may lead to a possible deviation of terrace age that cannot be ignored, and then lead to the misunderstanding of the spatial distribution characteristics of deformation rate. ③ The uncertainty related to the longitudinal profiles of river terraces. The ages and the heights above riverbed of different genetic terraces will show different spatial distribution characteristics along the river courses. For example, when the erosion wave caused by river capture extends upstream, i. e. retrogressive erosion, the age and the heights above riverbed of the resultant terraces will gradually decrease upstream, displaying upstream convergence. In this case, it should be careful to not only determine the terrace sequences of the target river by the correlation between the upstream and downstream terraces, but also examine the spatial pattern of deformation by utilizing the depth and rate of river incision. ④ The old geomorphic surfaces would be buried due to the relative subsidence in the anticlinal wing or the footwall of a fault. It would be difficult to accurately characterize deformation of the underlying structure (the anticline or the fault) by using such geomorphologic surfaces as the references. Understanding the above uncertainties of deformation rates deriving from fluvial geomorphological investigations is helpful for more reliable estimation of deformation rate and further revealing its spatiotemporal patterns as well as the mechanism of deformation.