With rising health-care expenditures and workforce shortages, sustainable alternatives to traditional outpatient follow-up strategies are required to optimise care efficiency. We aimed to investigate the cost-effectiveness and clinical effectiveness of patient-initiated follow-up (PIFU) supported by asynchronous telemedicine for patients with spondyloarthritis compared with usual care in daily practice. TeleSpA was a multicentre, pragmatic, open-label, randomised controlled trial. Patients with spondyloarthritis and stable disease were randomly assigned (1:1) to either the PIFU and asynchronous telemedicine group or usual care group. All patients received a scheduled outpatient visit at baseline and after 1 year. Patients were monitored remotely at 6 months (PIFU and asynchronous telemedicine) or at the discretion of the treating rheumatologist (usual care). The primary outcome was the number of rheumatology visits within a 1-year period. A trial-based 1-year health-economic evaluation from a Dutch health-care perspective (only including health-care costs) and societal perspective (also including travel costs and work productivity losses), per the Dutch guidelines was used to estimate cost-effectiveness. The safety analysis was done in the intention-to-treat population and was based on spontaneous reports of adverse events and serious adverse events or as observed by the research team. The primary analysis was in the intention-to-treat population. Individuals with relevant lived experience were involved in the study design. This trial was registered with the Dutch National Trial Register (NL71041.068.19) and ClinicalTrials.gov (NCT04673825) and is completed. Between Dec 2, 2020, and June 20, 2022, 200 patients were randomly assigned to PIFU and asynchronous telemedicine (n=100) or usual care (n=100). 79 (40%) of 200 participants were women, 121 (60%) were men, and the mean age was 55·0 years (SD 11·9). After 1 year, the mean number of rheumatology visits was 1·9 (SD 1·5) for the PIFU and asynchronous telemedicine group and 2·6 (1·3) in the usual care group (mean difference -0·7 [95% CI -1·0 to -0·3]; 25·4% reduction; p<0·0001). PIFU and asynchronous telemedicine was cost-effective from a health-care perspective, saving health-care costs (-€180 [95% CI -921 to 560]) without a loss in quality-adjusted life-years (0·004 [95 % CI -0·022 to 0·030]). Seven non-trial-related adverse events occurred in the PIFU and asynchronous telemedicine group and eight in usual care group (including one death). PIFU and asynchronous telemedicine resulted in significant and clinically meaningful reductions in rheumatology visits. This was not at the expense of health outcomes and saved health-care costs. Dutch Arthritis Society.