Aims To compare the long-term functional and anatomical outcomes of cataract surgery with combined versus 1-month deferred intravitreal dexamethasone implant (DEX) in eyes with pre-existing diabetic macular edema (DME). Methods Best-corrected visual acuity (BCVA) and central retinal thickness (CRT) were retrospectively evaluated in both groups before treatments, then 1, 4, 12 and 24 months after DEX. Results Forty eyes were analyzed, 20 in each group. BCVA disclosed comparable trends, increasing from similar starting values ( p  = 0.9913) to akin scores 1 month after DEX ( p  = 0.4229). After 4 months, it similarly reduced without significant variations within each group throughout the whole observation period. CRT was similar at the time of surgery ( p  = 0.6134) and was reduced by DEX injection in both samples, with a superior beneficial effect in the combined group after 1 month ( p  = 0.0010). At 4 months, CRT further elevated and remained overall stable in the long term without differences. By 12 months, 19 (95%) eyes received further injections: 1 (5%) fluocinolone, 3 (15%) received other DEX and fluocinolone, 13 (65%) ≥ 1 DEX only and 2 (10%) anti-VEGFs. During the second year, 6 additional eyes (from the 13 receiving DEX) switched to fluocinolone, reaching a total of 10 (50%). Similar results were observed in the deferred group. Conclusions DEX implant performed at the time of surgery achieved the same long-term functional and anatomical outcomes compared to a 1-month injection deferral in treating eyes with pre-existing DME that should undergo cataract extraction.