The aim of this study was to evaluate the effect of adding white mulberry (Morus alba L.) fruit to extruded corn snacks on their polyphenol profile, antioxidant properties, acetylcholinesterase (AChE) inhibitory activity and the preservation of phenolic compounds in an in vitro digestion model. Mixtures of corn grits with 0, 10, 15 and 20% dried mulberry fruit were extruded at temperatures of 100, 120 and 140 °C, and then the total polyphenol content (TPC) and antioxidant activity (IC50 for DPPH) were determined. For selected samples (0%, 140—3E; 15% mulberry, 140—9E; mulberry—13E), further antioxidant tests (FRAP, CUPRAC, Fe2+ chelation) were performed, the phenolic compound profile (UHPLC) and AChE inhibition were assessed, and a two-step in vitro digestion was conducted. The addition of mulberry significantly increased TPC- and free-radical-scavenging capacity compared to the control sample, with snacks containing 15% mulberry extruded at 140 °C showing approximately a 3.5-fold higher TPC than the control, while dried mulberry fruit itself exhibited about a five-fold higher TPC than this enriched snack. Among the snacks, the most favorable DPPH-radical-scavenging effect was obtained for the variant with 20% mulberry at 120 °C (IC50 = 0.176 mg/mL), whereas the mulberry fruit extract reached an IC50 of 0.0926 mg/mL. In a two-step in vitro digestion model, the mulberry-enriched snack with 15% fruit retained 69.3% of its initial TPC after the gastric phase and 33.3% after the intestinal phase, compared with 55.0% and 20.0%, respectively, for the control snack, confirming a partial but meaningful preservation of phenolic compounds under simulated gastrointestinal conditions. UHPLC analysis confirmed that mulberry and the enriched snacks are a rich source of chlorogenic acids and their isomers, as well as quercetin and kaempferol glycosides, which largely survived the two-step in vitro digestion, despite an observed decrease in TPC after the gastric stage and a further reduction after the intestinal stage. At the same time, mulberry extract and mulberry-enriched snacks exhibited high antioxidant activity in all tests conducted and in vitro AChE inhibitory activity, suggesting that Morus alba L. fruit has the potential to be used as a natural functional ingredient in the production of gluten-free snacks with antioxidant and potentially neuroprotective properties.