The increase in life expectancy at birth (e0) has stagnated since 2011 in England & Wales (E&W). Prior research hypothesized that the stagnation is related to increasing austerity measures and widening socio-economic inequalities. We formally assessed the contribution of education-specific mortality trends and increasing educational inequalities to the stagnation. We used individually-linked mortality data by sex, educational attainment (low, middle, high), and age (30+) from the ONS Longitudinal Study. We compared, by sex, the observed with the expected (= projected) increase in remaining life expectancy at age 30 (e30) in 2011–2017 for the national and education-specific populations. We assessed the education-specific mortality contributions using stepwise decomposition, and the contribution of increasing educational inequalities using a scenario analysis that assumes constant inequalities. In E&W in 2011–2017, e30 increased by 1.32 years (males) and 1.14 years (females) less than expected, which translates into 2.3 and 1.9 months annually. Stagnation of the increase in e30 occurred across all educational groups, with declines in e30 after 2011 for middle-educated males and low-educated females. Mortality trends among low-educated males (41.4%), middle-educated males (53.5%), and low-educated females (86.1%) contributed the most to the sex-specific stagnation. The observed increases in educational inequalities between 2011 and 2017 contributed approximately 27% to the national e30 stagnation.Widening educational inequalities, and particularly the unfavourable mortality trends observed for middle educated males and low educated females since 2011, contributed substantially to the e30 stagnation since 2011 in England & Wales.