The objective was to describe the impact of socioeconomic inequalities (SEI) on the prevalence and incidence of pharmacologically treated type 2 diabetes (T2D) in mainland France over the 2010–2020 period. Cases of diabetes were identified using a validated algorithm in the national health data system among adults aged 45 and older. SES was measured using the social deprivation index (FDep, by population quintiles; Q1: reference corresponding to the most advantaged municipalities) for mainland France. The relative risks (RR) of having T2D (prevalence) and of developing T2D (incidence) in Q2, Q3, Q4, and Q5 were estimated by sex over the period using Poisson regression. A positive gradient was observed in the RR of T2D prevalence and incidence according to FDep quintiles regardless of the year. The influence of the ISE on T2D prevalence increased over the period for men in Q2, Q3, Q4, and Q5, and for women in Q3, Q4, and Q5. For example, the RR of prevalence for Q5 vs. Q1 increased from 2010 to 2020 from 1.399 [95% CI: 1.394; 1.403] to 1.532 [95% CI: 1.527; 1.536] among men, and from 1.798 [95% CI: 1.791; 1.804] to 1.916 [95% CI: 1.909; 1.922] among women. For incidence, the RR increased only among men in Q4 and Q5. For example, the incidence RR for Q5 vs. Q1 increased from 2012 to 2020 from 1.548 [95% CI: 1.523; 1.573] to 1.667 [95% CI: 1.652; 1.681] among men and from 1.912 [95% CI: 1.876; 1.948] to 1.948 [95% CI: 1.929; 1.968] among women. Socioeconomic indicators are positively associated with the prevalence and incidence of T2D in France, with a stronger association observed among women. These disparities increased between 2010 and 2020, for prevalence in both sexes and for incidence among men.