Objectives: Sleep quality may impact symptom experience in Irritable Bowel Syndrome (IBS). Our aim was to investigate the relationship between sleep quality and gastrointestinal (GI) symptoms using actigraphy and the Experience Sampling Method (ESM). Methods: IBS patients were recruited from a tertiary Neurogastroenterology clinic and the community. GI symptoms and mood were recorded on a smartphone application, ten times per day, over seven consecutive days. Subjective sleep quality was recorded every morning to reflect the night before. Objective measures of sleep quality were estimated from wrist-worn actigraphy. Cross-lagged structural equation models were built to assess the directionality of sleep-symptom relationships over time. Results: Eighty IBS patients completed the study (mean age: 37 (range 20 – 68), 89% female, 78% community). Sixty-six % had a Pittsburgh Sleep Quality Index (PSQI) score ≥ 8 indicating a clinically significant sleep disturbance. Eighty-two % (95% CI: 72-90) screened positive for a sleep disorder, most commonly insomnia. In cross-lagged analysis, poor subjective sleep quality predicted next day abdominal pain (0.036 < p < 0.040) and lower GI symptoms (0.030 < p < 0.032), but not vice versa. No significant relationship with GI symptoms was found for any objective sleep measure using actigraphy. Conclusions: Poor subjective sleep quality was associated with higher next day lower GI symptom levels, but not vice versa. Objective sleep measures did not predict next day abdominal symptoms, potentially supporting the conclusion that it is the perception of sleep quality which is most influential. This study may be used to guide future research into the effect of sleep interventions on GI symptoms.