Background Both internet-based cognitive-behavioural therapy (ICBT) and physical exercise are alternatives to treatment as usual (TAU) in managing mild to moderate depression in primary care. Aims To determine the cost-effectiveness of ICBT and physical exercise compared with TAU in primary care. Method Economic evaluation of a randomised controlled trial (N=945) in Sweden. Costs were estimated by a service use questionnaire and used together with the effects on quality-adjusted life-years (QALYs). The primary 3-month healthcare provider perspective in primary care was complemented by a 1-year societal perspective. Results The primary analysis showed that incremental cost per QALY gain was (sic)8817 for ICBT and (sic)14 571 for physical exercise compared with TAU. At the established willingness-to-pay threshold of (sic) 21 536 ( pound 20 000) per QALY, the probability of ICBT being cost-effective is 90%, and for physical exercise is 76%, compared with TAU. Conclusions From a primary care perspective, both ICBT and physical exercise for depression are likely to be cost-effective compared with TAU. (c) The Royal College of Psychiatrists 2018.