To analyse average lifespan and quantify the effect of avoidable/amenable mortality on the difference between state-specific mortality and a low-mortality benchmark in Mexico during 1990-2015. Retrospective cross-sectional demographic analysis using aggregated data. Vital statistics from the Mexican civil registration system. Aggregated national data (from 91.2 million people in 1995 to 119.9 in 2015) grouped in 64 populations (32 Mexican states (including Mexico City) by sex) with cause-of-death data. Cause-specific contributions to the gap in life expectancy with a low-mortality benchmark in three age groups (0-14, 15-49 and 50-84 years). Infants and children under the age of 15 years show improvements towards maximal survival in all states. However, adult males aged 15 to 49 years show deterioration after 2006 in almost every state due to increasing homicides, and a slow recovery thereafter. Out of 35 potential years, females and males live on average 34.57 (34.48 to 34.67) and 33.80 (33.34 to 34.27), respectively. Adults aged 50 to 84 years show an unexpected decrease in the low mortality benchmark, indicating nationwide deterioration among older adults. Females and males in this age group show an average survival of 28.59 (27.43 to 29.75) and 26.52 (25.33 to 27.73) out of 35 potential years, respectively. State gaps from the benchmark were mainly caused by ischaemic heart diseases, diabetes, cirrhosis and homicides. We find large health disparities between states, particularly for the adult population after 2005. Mexico has succeeded in reducing mortality and between-state inequalities in children. However, adults are becoming vulnerable as they have not been able to reduce the burden of violence and conditions amenable to health services and behaviours, such as diabetes, ischaemic heart diseases and cirrhosis. These trends have led to large health disparities between Mexican states in the last 25 years.