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Geraniol is an acyclic monoterpene alcohol with well-known anti-inflammatory and antimicrobial properties which has shown eubiotic activity towards gut microbiota (GM) in patients with irritable bowel syndrome (IBS). Methods: Fifty-six IBS patients diagnosed according to Rome III criteria were enrolled in an interventional, prospective, multicentric, randomized, double-blinded, placebo-controlled trial. In the treatment arm, patients received a low-absorbable geraniol food supplement (LAGS) once daily for four weeks. Results: Patients treated with LAGS showed a significant reduction in their IBS symptoms severity score (IBS-SSS) compared to the placebo (195 vs. 265, <i>p</i> = 0.001). The rate of responders according to IBS-SSS (reduction ≥ 50 points) was significantly higher in the geraniol vs placebo group (52.0% vs. 16.7%, <i>p</i> = 0.009) mainly due to the IBS mixed subtype. There were notable differences in the microbiota composition after geraniol administration, particularly a significant decrease in a genus of <i>Ruminococcaceae, Oscillospira</i> (<i>p</i> = 0.01), a decreasing trend for the <i>Erysipelotrichaceae</i> and <i>Clostridiaceae</i> families (<i>p</i> = 0.1), and an increasing trend for other <i>Ruminococcaceae</i> taxa, specifically <i>Faecalibacterium</i> (<i>p</i> = 0.09). The main circulating proinflammatory cytokines showed no differences between placebo and geraniol arms. Conclusion: LAGS was effective in treating overall IBS symptoms, together with an improvement in the gut microbiota profile, especially for the IBS mixed subtype.