Vortex-induced vibration (VIV) is one of the main causes of fatigue failure of submarine pipelines under the action of ocean currents. A reasonable estimation for the allowable (maximum) length of a pipeline span is vital for avoidance of VIVs. The length of a pipeline span can alter its natural frequency and further influence the corresponding critical reduced velocity for the onset of VIVs. Nevertheless, the experimental observations indicated that the VIV hysteresis could be significant under the natural flows with increasing-decreasing velocity cycles, especially under the wall-proximity conditions. A case study is then performed to examine VIV hysteresis effects on the allowable span length of submarine pipelines. A dimensionless parameter is proposed and derived for characterizing such hysteresis effect on the allowable span length. It is indicated that lower-critical span lengths are much smaller (up to more than 20%) than those estimated with the commonly-used upper-critical flow velocity. As such, the VIV hysteresis effect should be taken into account for determining the allowable span length of submarine pipelines.