The characteristics of a native starch limit its application in the food industry; for this reason, it is important to investigate alternatives for obtaining modified starches with better characteristics and more possibilities of application. Oca (Oxalis tuberosa) starch was subjected to annealing process with a temperature of 42 and 50°C and starch:water ratios of 1:6 and 1:2 during 24 hr. The effects of the annealing process on thermal, structural, and rheological properties were investigated. The annealing at 50°C and 1:6 (starch:water) ratio yielded a starch with high peak viscosity, stability ratio, gelatinization temperature, and gel firmness, but low solubility and low swelling power. All annealed starch gels had a more elastic behavior (G′ > G″), lower viscosity and greater stability to retrogradation compared to native starch. The annealing process caused the rearrangement of amylopectin and amylose in the starch granule, obtaining a more orderly structure, which increased the thermal stability and functional properties of oca starch. Practical applications: Few studies have been reported on chemical, physical, or enzymatic modification of native starches using the annealing process, none on oca starch. The annealing process improves the thermal stability and functional properties of oca starch, which can expand its application in the food industry. The starch produced in this work can be used as raw material for noodles, gluten-free bakery products, and as a thickening agent.