Abstract Background Low back pain (LBP) is a world leading cause of disability and has substantial impact on individuals and society as a whole. The largest part of the societal burden of LBP is caused by indirect costs, including sick leave. Aims We aimed to describe occupational recovery and associated costs for workers consulting an occupational physician (OP) with LBP, and to determine to what extent this differs by diagnoses: non-specific favourable LBP, non-specific unfavourable LBP, lumbosacral radicular syndrome (LRS) and specific LBP. Methods We analysed longitudinal dynamic cohort data from an occupational health service, representing ~1.2 million workers from various companies and sectors throughout the Netherlands. The OP registered data on sick leave and LBP diagnoses. A survival analysis was performed on sick leave duration to determine recovery and a linear regression analysis on cost per episode, adjusting for sex, age and working hours. Results We analysed 5951 LBP episodes from 5472 workers who consulted an OP, with a median and mean duration sick leave of 95 and 151 days, respectively. The probability of not recovering was 82% at 30 days and 10% at 1 year. The mean cost per episode was €15 350. Specific LBP (€22 999; beta (95% confidence interval [CI]): 16 278 (13 325–19 165)) and LRS (€20 111; beta (95% CI): 13 589 (12 527–14 659)) had the longest and most costly episodes, compared to non-specific favourable LBP (€6745; reference group). Conclusions With LRS and non-specific unfavourable LBP accounting for over 83% of LBP-associated sick leave costs, the work-directed care of workers with these two diagnoses deserves increased attention.