In this study, we initially assessed the antioxidant activities of various HG-type hawthorn pectin-iron(III) complexes, which were synthesized in our previous research, utilizing methods such as reducing assay, 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and scavenging, and hydroxyl radical scavenging. The results showed that the antioxidant capacity of the hawthorn pectin iron(III) complexes exhibited a positive correlation with increasing concentrations, ranging from 0.2 to 1.0 mg/mL. Notably, the pectin complex chelated with iron via ultrasonic extraction and de-esterification for 20 min (designated as DU20-Fe) showed the most significant antioxidant activity. Subsequently, DU20-Fe was chosen for in vivo activity assessment in a mouse model of iron-deficiency anemia (IDA). The findings indicated that DU20-Fe significantly enhanced levels of red blood cells (RBC), mean corpuscular volume (MCV), and mean corpuscular hemoglobin (MCH) content in the mice with IDA. Furthermore, histological analysis of the liver demonstrated that DU20-Fe effectively alleviated liver damage in the IDA mice. These results validate the potential of hawthorn pectin-iron complexes in exhibiting anti-iron-deficiency anemia activity, suggesting that the hawthorn pectin-iron(III) complex may be developed into a bio-polysaccharide-based iron supplement with multiple health benefits.