Helicobacter pylori, a gastric carcinogenic pathogen, colonizes the stomach of 50% of the human population and is considered as a WHO priority 2 due to its antibiotics resistance. Therefore, research should aim to avoid H. pylori infection. Probiotics are an emerging alternative to handle this pathogen, making it necessary to have means to evaluate their effectiveness. This work evaluated the effect of a carrageenan encapsulated probiotic, Lactobacillus fermentum UCO-979C strain, against the pathogenic H. pylori SS1 strain under simulated gastric conditions (fasting or standard diet, pH 3.0 under microaerophilic condition and agitation). Samples were obtained from simulators up to 2.5 h after adding the probiotic, either planktonic or carrageenan encapsulated, and H. pylori were counted using enriched Columbia agar. Gastric simulations under fasting or standard diet showed collaboration between L. fermentum and carrageenan against the pathogen, it is undetectable at 1.5 or 2.5 h, respectively, allowing to conclude that the administration of the probiotic under fasting (harsher acid environment) provides a better anti-H. pylori effect that administering it associated with the diet. Thus, it can be suggested to consume low pH resistant probiotics under fasting. Copyright © 2018. Published by Elsevier Ltd.