Poor compliance with conventional asthma medications remains a major problem in achieving asthma control. Nigella sativa oil (NSO) is used traditionally for many inflammatory conditions such as asthma. We aimed to investigate the benefits of NSO supplementation on clinical and inflammatory parameters of asthma. NSO capsules 500mg twice daily for 4 weeks was used as a supplementary treatment in a randomised, double-blind, placebo-controlled trial (RDBPCT) in asthmatics (clinicaltrials.gov: NCT02407262). The primary outcome was Asthma Control Test (ACT) score. The secondary outcomes were pulmonary function test, blood eosinophils, and total serum Future studies should follow asthmatics for longer periods in a multicentre trial.