•Mean NPI/NPI-Q ratings were higher in converters versus in non-converters.•The overall standardized mean difference (SMD) approached significance.•Effects especially strong in studies with > 2 years of follow-up.•Effects were also strong in a study with a mean age of >80 years.•Our results suggest that NPI/NPI-Q ratings predict conversion from MCI to dementia. Neuropsychiatric Symptoms (NPS) are common in Mild Cognitive Impairment (MCI). The Neuropsychiatric Inventory (NPI) and its shorter version, the Neuropsychiatric Inventory Questionnaire (NPI-Q), are the most common measures to assess NPS. Our objective was to determine if NPI/NPI-Q ratings predict conversion from MCI to dementia. Empirical longitudinal studies published in English or Spanish, concerned with the role of NPS as a risk factor for conversion from MCI to dementia, with a diagnosis of MCI following clinical criteria, that reported NPI/NPI-Q total score in converters versus non-converters, were included. Random effects models were used, and heterogeneity was explored with stratification and a random-effects meta-regression. The overall conversion rate and the standardized mean difference (SMD) for evolution, as a function of NPI/NPI-Q scores, were calculated. The overall conversion rate was 35 %. Mean NPI/NPI-Q ratings were higher in converters versus in non-converters, with the overall SMD approaching significance. Heterogeneity was observed in studies of more than two years of follow-up and in a study with a mean age of more than 80 years. This heterogeneity concerned the size, not the direction of the difference. Our results suggest that NPI/NPI-Q ratings are associated with conversion from MCI to dementia.