Weaning stress frequently compromises intestinal integrity and nutrient absorption in piglets and induces structural perturbations in the gut microbiota. This study investigated the effects of dietary Paramylon, a linear β-1,3-glucan from Euglena gracilis, on growth and intestinal function. A total of 32 healthy, 21-day-old weaned piglets (male, castrated, Duroc × Landrace × Yorkshire) were randomly allocated to four groups: control, 0.025%, 0.05%, and 0.1% Paramylon (8 pigs/group). The results showed that 0.05% dietary Paramylon quadratically increased average daily gain and feed intake (p < 0.05). Serum TC content significantly increased, while the serum urea level significantly decreased (p < 0.05). This optimal dose was used for mechanistic exploration. Dietary 0.05% Paramylon notably enhanced ileal morphology, increasing the villus height to crypt depth ratio (p < 0.01) and significantly improving apparent nutrient digestibility and ileal β-amylase activity (p < 0.05). The expression levels of SLC7A1 and GLUT2 in ileum tissues were significantly upregulated (p < 0.05). The expression level of SLC7A7 in the liver was also increased (p < 0.05). This nutrient transport-promoting effect was further confirmed in IPEC-J2 cells, which manifested because 10 ng/mL of pure Paramylon significantly upregulated the gene expressions of SLC38A2, EAAT3, PEPT1, and GLUT2 (p < 0.05). KEGG enrichment analysis on the ileum indicated that differentially abundant metabolites were enriched in amino acid-related metabolic pathways. Furthermore, the 16s sequencing results revealed that Romboutsia was significantly enriched in the Paramylon group. In conclusion, Paramylon, as an effective dietary supplement, helps promote nutrient digestion and absorption in weaned piglets and contributes to maintaining intestinal health.