This paper describes a research project using a single-case experimental design (A-B-A), which aimed to explore the impact of sensory integration therapy (SIT) on level of engagement and maladaptive behaviour (measured through timed scores) and function (using Goal Attainment Scaling, GAS) for five learning disabled adults with tactile sensory modulation disorder. Each phase lasted 4 weeks and consisted of 24 measurements in total. Individually tailored SIT was given twice weekly for 4 weeks during the intervention phase (B), immediately prior to each individual's participation in his or her prescribed horticulture task. The changes between phases in engagement, maladaptive behaviours and function scores, measured as the difference between baselines and intervention, were analysed visually and statistically for each participant. The intervention produced significant improvements in engagement for participant four, with a highly significant deterioration in scores for all five participants on withdrawal of SIT. All the participants' maladaptive behaviour decreased significantly on the introduction of SIT. Although there was no significant change to GAS scores for four participants, participant four's score improved significantly with SIT. The withdrawal of SIT resulted in a highly significant deterioration in GAS scores for participants one, two, four and five. This study may be the first to suggest that SIT is effective in improving functional performance in adults with a learning disability with a tactile sensory modulation disorder.