Serotransferrin cDNA from the Siberian sturgeon Acipenser baerii was isolated and its expression patterns during early life intervals were characterized. It contained an ORF encoding a 708-aa-long polypeptide, including a 19-aa signal peptide. Bioinfomatic analysis and 3D modeling indicated a typical bi-lobal structure with conserved iron-coordinating residues. During embryonic development, the potential transition of maternally provisioned transcripts to zygotically de novo transcribed ones occurred around blastula stage. The transferrin mRNA levels peaked at stages responsible for pronephros, heart and erythropoietic component differentiation. After hatching, the transferrin mRNA expression gradually increased at early ontogenic phases (0 to 3 DPH) corresponding to the periods in which prolarvae exhibited increased blood circulation and liver differentiation. The expression decreased at subsequent stages in which prolarvae exhibited benthic movement. The tissue distribution assay indicated liver-predominant expression at fingerling stage. From the microinjection-based challenge with Aeromonas hydrophila at day-0 and day-7, the transcriptional response was modulated toward upregulation, in which the amounts induced at 6, 12 and 24 HPI were greater in prolarvae injected at day-7 than at day-0. Therefore, transferrin plays important roles in both early development and host protective responses to pathogens in the Siberian sturgeon.