Background <p>Physical activity, sedentary behaviour, and sleep were shown to be independently associated with low back pain (LBP). The aim of this cross-sectional study was to explore the associations between 24-hour movement behaviour compositions and the occurrence, severity, and estimated level of LBP impact on an individual’s life.</p> Methods <p>A convenience sample of 197 adults (40% females, 37 ± 11 years of age) were asked to wear an activPAL accelerometer for at least 7 consecutive days to assess their time-use composition consisting of moderate- to vigorous-intensity physical activity (MVPA), light-intensity physical activity (LPA), sedentary behaviour (SB), and sleep and to complete a questionnaire on LBP and sociodemographic characteristics. Compositional isotemporal substitution analyses were conducted separately for the non-domain-specific and domain-specific (including occupational and non-occupational domains) movement behaviour compositions.</p> Results <p>Reallocating time from MVPA to any other movement behaviour or from sleep to LPA was associated with a higher LBP impact score. For example, reallocating 60&#xa0;min/day from MVPA to LPA was associated with on average 17 points (95% CI: 6 to 28) higher LBP impact score (on a 0–70 scale). We did not find significant associations between the domain-specific time-use composition and LBP impact score (<i>p</i> = 0.060). We also did not find significant associations of the time-use compositions with occurrence and severity of LBP (<i>p</i>-value range: 0.067 to 0.649).</p> Conclusion <p>Our study suggests that LBP sufferers with higher MVPA and sleep better cope with LBP. The differences in the LBP impact scores associated with theoretical reallocations between movement behaviours may be deemed clinically important. Future longitudinal and experimental studies in population-representative samples are needed to confirm our findings.</p>