The mitral-aortic intervalvular fibrosa (MAIF) is involved in the functional integrity of the two valves. We discuss the clinical decision-making in a population with MAIF pseudoaneurysms following valve replacement surgery. From 2003 to 2010, 16 patients (age 65 ± 17 years) were referred to our institute with worsening valvular disease. All the patients had undergone previous aortic or mitral valve replacement surgery. Transthoracic and transesophageal echocardiography was performed in these patients. According to the echocardiographic findings, we described two groups of patients with MAIF pseudoaneurysms: group 1 (seven patients) without previously known infective disease, and group 2 (nine patients) with a medical history of endocarditis. For asymptomatic patients without an infective background or valve regurgitation (group 1), clinical and echocardiographic follow-up was selected. Reintervention was planned for postinfection pseudoaneurysms (group 2), on account of the residual paravalvular leak and the high-risk of MAIF rupture. The case series emphasizes the need for more awareness about MAIF pseudoaneurysms, rare complications of aortic and mitral valve surgery, which occur far more frequently than expected. Although clinical decision-making is debatable, it may be helpful to differentiate patients into those with or without previous endocarditis, and according to heart failure symptoms.