A late onset frontal lobe syndrome (LOF) refers to a clinical syndrome with apathy, disinhibition, or stereotypical behavior arising in middle or late adulthood. Diagnostics are challenging, and both clinicians and patients need reliable predictors of progression to improve clinical guidance. In this longitudinal multicenter and genetically screened prospective study, 137 LOF patients with frontal behavior (FBI score≥11) and/or stereotypical behavior (SRI≥10) were included. Progression was defined as institutionalization, death, or progression of frontal or temporal atrophy at magnetic resonance imaging (MRI) after two years of follow up. Absence of progression at MRI in addition to stable or improved Mini Mental State Examination and Frontal Assessment Battery scores after two years was indicative for non-progression. The presence of stereotypy and a neuropsychological profile with executive deficits at baseline were found to be predictive for progression, while a history and family history with psychiatric disorders were predictors for non-progression. The combination of these clinical markers had a predictive value of 80.4% (p < 0.05). In patients presenting with late onset behavioral symptoms, an appraisal of the rate of deterioration can be made by detailed mapping of clinical symptoms. Distinction of progressive discourses from non-progressive or treatable conditions is to be gained.