Crabs are important components of benthic fauna of tidal marsh ecosystem. Grazing on living salt marsh plant leaves and causing nest failure of birds nesting on tidal marsh plants indicate that crabs could climb on salt marsh plants. However, plant-climbing behavior of tidal marsh crabs is poorly understood. Chiromantes neglectum, which was formerly identified as C. dehaani in Changjiang River estuary while C. dehaani actually distributes in coastal wetlands of south China (see Komai et al. 2013 for details), is a dominant zoobenthic species of tidal marshes of Changjiang River estuary. We studied the diel plant-climbing behavior of the mudflat crab, C. neglectum, in a Phragmites-dominated tidal marsh in Changjiang River estuary through directly observing and estimating diel variation of densities of crabs on reed shoots and marsh surface. We used Generalized Linear Mixed Models (GLMM) to analysis the effects of sample sites, observation dates, observation time and combinations of these factors on total crab density (the sum of climbing crab density and marsh surface crab density), climbing crab density, marsh surface crab density and percent of climbing crabs (climbing crab density/total crab density). Bonferroni test was used to analysis the differences among observation times and also observation dates. We found significant diel variations of both climbing crab density and marsh surface crab density (Fig. 1 and Table 1, all P < 0.05). Combining the diel variations of both climbing crab density and marsh surface crab density and field observations, it revealed that most C. neglectum individuals began to climb on reed shoots after dusk (17:00–19:00) and come down to marsh surface from reed shoots before dawn (5:00–7:00) (Fig. 1). There was a significant diel variation for the ratio of climbing crab density to total crab density (Figure 1 and Table 1, P < 0.05). The percent of climbing crabs was higher during the nighttime (from 0.16 to 0.34 during 19:00–5:00) than during the daytime (from 0.02 to 0.15 during 5:00–19:00) (P < 0.05). The total crab density varied significantly among observing bouts (P < 0.05) with significantly higher total density during the nighttime than the daytime, indicating that C. neglectum individuals were prone to using burrows during the daytime, thus had a diel movement pattern among burrow, marsh surface and reed shoots. Furthermore, we found significant differences among observing dates for total crab density, climbing crab density, marsh surface crab density and percent of climbing crabs (Fig. 2 and Table 1, all P < 0.05). It seems that plant-climbing behavior of C. neglectum was related to grazing on leaf blades of reed shoots and affected by the diel variation of light intensity. Further studies are needed to reveal what factors and how these factors affect plant-climbing behavior of C. neglectum and how plant-climbing behavior of C. neglectum relate to ecological processes of salt marsh ecosystems.