The figure is one percentage point higher than the year before, when 23.4% of the population was considered at risk of poverty or social exclusion.
It marks a significant deterioration of the social landscape in Europe as the economic crisis continues to bite.
The highest shares were recorded in Bulgaria (49%); Romania and Latvia (both 40%); Lithuania (33%); and Greece and Hungary (both 31%). The lowest were in the Czech Republic (15%), the Netherlands and Sweden (both 16%), and Luxembourg and Austria (both 17%).
At risk of poverty
Overall, 17% of the EU's total population were considered at-risk-of-poverty, meaning their disposable income was below 60% of the national average, after social security transfers.
The highest rates in that category were recorded in Bulgaria, Romania and Spain (all 22%) and Greece (21%).
"It is important to note that the at-risk-of-poverty rate is a relative measure of poverty and that the poverty threshold varies greatly between member states," Eurostat said in a note.
"The threshold varies also over time and in a number of member states it has fallen in recent years due to the economic crisis," added the EU statistical office.
In related statistics, 9% of the EU population were considered as "severely materially deprived", meaning they were struggling to pay their rent or utility bills and could not afford taking one week holiday from home.
Some 10% were living in households with "very low work intensity", where adults worked less than 20% of the time. Belgium had the highest rate in that category, with 14%.
Reducing the number of persons at risk of poverty or social exclusion in the EU is one of the key targets of the 'Europe 2020' strategy for growth and jobs.