This study investigated the effects of sodium hydroxide activation and ground granulated blast-furnace slag addition on the mechanical behavior and compressibility of iron ore tailings. The novelty of the study lies in the integrated evaluation of NaOH concentration, GGBFS content, curing time, and confining pressure. NaOH concentrations of 0, 1, 3, and 5 M and GGBFS contents of 0, 3, 6, and 9 wt.% were investigated. Standard compaction tests, unconsolidated undrained triaxial tests under confining pressures of 100, 200, and 300 kPa, one dimensional consolidation tests, and scanning electron microscopy were conducted. The triaxial specimens were tested at their as cured moisture condition after 7 and 28 days of curing. At a confining pressure of 200 kPa and a NaOH concentration of 5 M, increasing GGBFS content from 0 to 9% increased the peak deviator stress from 1,265 to 5,824 kPa. Extending curing from 7 to 28 days increased the peak deviator stress of the specimen containing 9% GGBFS and 1 M NaOH from 1,816 to 6,260 kPa. The maximum apparent cohesion and friction angle were approximately 750 kPa and 51.61°, respectively. The compression and unloading indices decreased from 0.651 and 0.032 in the untreated specimen to 0.032 and 0.007 in the mixture containing 3 M NaOH and 9% GGBFS. SEM observations showed broader particle contacts and more continuous regions in the stabilized specimens, particularly in the mixture containing the higher GGBFS content. The combined treatment increased strength and reduced volumetric deformation.