The gut microbiota is one of the key elements responsible for maintaining the body’s homeostasis. Its diverse composition affects, among others, the digestive and immune systems and also the circulatory system. Imbalances within the microbial community, referred to as dysbiosis, may lead to increased intestinal barrier permeability, chronic inflammation, and abnormal immune responses, which can be associated with the development of numerous diseases. Gut dysbiosis results in disturbances in the production of short-chain fatty acids, which exert anti-inflammatory effects, regulate blood pressure, and inhibit cardiac fibrosis. At the same time, it promotes the increased synthesis of trimethylamine N-oxide, a metabolite linked to inflammation, endothelial dysfunction, a higher risk of thrombosis, and the occurrence of arrhythmias. Additionally, small intestinal bacterial overgrowth (SIBO) may increase inflammation and contribute to metabolic and cardiovascular diseases (CVDs). The gut microbiota also influences the immune system through the production of neurotransmitters and modulation of T-cell activity, which may play a role in the development of autoimmune diseases. Reduced microbial diversity and an increased abundance of pathogenic bacteria are observed in individuals with hypertension and CVD, underscoring the importance of the microbiota as both a preventive and therapeutic factor. These findings highlight the crucial role of the gut microbiota in maintaining cardiovascular health and emphasize the need for further research into its modulation in the treatment of chronic diseases.