Lower back pain is highly prevalent globally, yet the aetiology is poorly and incompletely understood. Lower back pain is common among those with a history of frequent cyclic combined loading, such as long-haul and shorthaul truck drivers and high-speed watercraft operators. Characterization of the viscoelastic behaviour of the lumbar spine will improve understanding of lower back pain, provide data for computational models of the lumbar spine, and inform injury prediction models. Ten osteoligamentous porcine functional spinal units were mechanically tested until primary soft tissue failure using a cyclic combined flexion-compression loading profile. Displacement and force data were then fit to a quasilinear viscoelastic model with two time constants (24.6s and 575s), three creep coefficients, and two instantaneous elastic parameters. Results indicated a very good fit from experimental data to model data (R² = 0.997 ± 0.003), largely dominated by the steady-state and slow rate creep coefficients. Quasilinear viscoelastic (QLV) modelling appears to be a suitable method for modelling porcine lumbar spine viscoelastic behaviour.