•Long-term mechanical properties of BS including the duration of load (DOL) and creep effects were investigated.•The DOL effect of BS was more severe than that of other structural wooden materials.•The time-dependent constitutive models of DOL and creep effects for BS were developed. Bamboo scrimber (BS), a main bamboo composite, has wide application prospects in green buildings. As a viscoelastic biomass material, long-term mechanical properties are the key indicators for its safe lifetime service. In this study, both short-term and long-term tension tests parallel to grain of BS were conducted. The long-term mechanical properties of BS including the duration of load (DOL) and creep effects were investigated from the macro and micro levels. Results indicated that the DOL effect of BS was more severe than other structural wooden materials, but its relative creep strain was smaller. From microlevel characterization, the DOL effect was strongly correlated with its microfracture morphology and bamboo fiber damage, while the creep effect was related to the decomposition of hemicellulose. Finally, time-dependent constitutive models were developed and provided good prediction for the DOL factor and creep strain of BS under different load durations. This study was beneficial for the long-term safe application of BS as a new structural material.