The study was aimed at examining the reliability of the Double Inclinometer (DI) method for the assessment of thoracolumbar Range of Movement (ROM) and Joint Position Sense (JPS) in patients with a recent history of Low Back Pain (LBP). Twenty patients with a history of LBP in the last three months participated. The thoracolumbar ROM and JPS were examined from a standing position by using both the DI and the tape measure method. The DI method was found to have moderate to good intra-rater (ICC = 0.68–0.79, SEM = 2.20–2.77°, SDD = 6.09–7.67°), moderate inter-rater (ICC = 0.59–0.62, SEM = 2.96–3.35°, SDD = 8.19–9.27°) and poor test-retest reliability (ICC = 0.13–0.17, SEM = 3.98–4.32°, SDD = 11.02–11.96°) for the assessment of thoracolumbar JPS. For the assessment of thoracolumbar ROM, the DI method was found to have good to excellent intra-rater (ICC = 0.88–0.94, SEM = 4.25–6.20°, SDD = 11.77–17.17°), excellent inter-rater (ICC = 0.90–0.91, SEM = 7.26–7.74°, SDD = 20.11–21.43°) and excellent test-retest reliability (ICC = 0.91–0.93, SEM = 6.03–6.87°, SDD = 16.70–19.02°). The concurrent validity of the DI method with the tape measure method was found to be very weak for the assessment of thoracolumbar JPS (r = 0.02, p = 0.93) and strong for the assessment of thoracolumbar ROM (r = 0.66, p = 0.001). The DI method seems to be a very reliable method for the assessment of thoracolumbar ROM in individuals with a recent history of LBP.