<p>Post-weaning piglets often face digestive challenges and growth setbacks due to gut microbiota imbalances and increased susceptibility to infections and diarrhea. Various alternatives to antibiotic growth promoters have been proposed, including synbiotic supplements. Maple syrup is a source of prebiotic compounds, while <i>Bacillus velezensis</i> FZB42 is a nonpathogenic microorganism with probiotic potential. Therefore, this study investigated the effects of a fermented ingredient combining maple syrup and <i>B. velezensis</i> as a potential synbiotic. The focus was on growth performance, occurrence of diarrhea, short-chain fatty acid production, and intestinal microbiota composition in weaned piglets. A two-week experiment in a randomized complete block design was conducted with the following treatments: a negative control diet (NC); a positive control diet containing chlortetracycline hydrochloride (PC); a synbiotic supplement containing maple syrup and <i>B. velezensis</i> (SYN); and a freeze-dried maple syrup supplement (FMS). Compared to the NC group, SYN supplementation increased final body weight, average daily gain, and decreased the feed conversion ratio (<i>p</i> &lt; 0.05). The results showed that dietary supplementation with SYN supplement increased butyric acid concentrations in the ileum compared to NC (<i>p</i> &lt; 0.014) and increased acetic (<i>p</i> &lt; 0.001) and butyric acids (<i>p</i> &lt; 0.044) in the colon compared to PC treatment. Additionally, both maple syrup-based supplements favorably modulated the relative abundance of microbial taxa, increasing <i>Oscillisibacter</i> and reducing <i>Campylobacter</i>, among others. Our findings indicate that dietary supplementation with a synbiotic composed of <i>B. velezensis</i> FZB42 and maple syrup improved the growth performance of weanling piglets, increased acetic and butyric acid content in the colon and butyric acid in the ileum, and favorably modulated the intestinal microbiota.</p>