Probiotics have been suggested to be effective for functional dyspepsia, but their effect on gastric motility is not clear. We evaluated the effect of OLL2716 (LG21 strain) on mild to moderate delayed gastric emptying by a double-blind, parallel-group, placebo-controlled, randomized trial. Participants ( = 28) were randomly assigned to ingest LG21 strain-containing yogurt (LG21 strain group) or LG21 strain-free yogurt (placebo group) for 12 weeks. The C gastric emptying breath test was performed to measure the gastric emptying rate over time following ingestion of a liquid meal, and the time to reach the peak (Tmax) was used as an indicator of gastric emptying. We also measured the salivary amylase concentration, an indicator of autonomic dysfunction under stress. The per-protocol population ( = 27, male = 4, female = 23) was evaluated for efficacy. When a ≥30% reduction in the difference between participant's Tmax and the Japanese mean Tmax was defined as an improvement, the odds ratio of improvement in delayed gastric emptying compared to placebo after 12 weeks was 4.1 (95% confidence interval, 0.8 to 20.2). Moreover, salivary amylase concentrations were significantly lower than in the placebo group, indicating an improvement in autonomic function. The present data were not enough to support the beneficial effects of the LG21 strain on delayed gastric emptying. However, if we define the odds ratio in further study investigated with a larger number of participants, LG21 strain might be expected to have some impact on delayed gastric emptying.