Introduction: Lactose intolerance (LI) is characterized by specific gastrointestinal symptoms following the consumption of dairy products and lactose-containing foods, symptoms that may also be experienced by individuals with intestinal methanogenic overgrowth (IMO). However, such clinical manifestations may be modulated by the use of probiotics; the aim of this study was to analyze the preliminary efficacy of a probiotic formulation on gastrointestinal symptoms in adults with LI and IMO. Materials and Methods: A randomized, double-blind, placebo-controlled pilot study was conducted with 22 adults who tested positive on a hydrogen breath test (HBT); they were assigned to intervention or placebo groups based on their diagnosis. Accordingly, they completed a Questionnaire on symptoms of Lactose Intolerance (QSLT) and underwent successive nutritional assessments.