An efficient α‐sialylation methodology for various primary, secondary, and tertiary alcohol acceptors has been developed. The sialic acid ethyl thioglycoside 1b, bearing a 4‐nitropicoloyl moiety as the stereodirecting group at the C4 position, was utilized as the glycosyl donor, and the sialylation reaction was activated with N‐iodosuccinimide and catalytic triflic acid in a 1:1 mixture of dichloromethane/acetonitrile as solvent. The method was successfully applied to the stereocontrolled synthesis of protected trisaccharide 11 found in the repeating unit of serotype Ia Group B Streptococcus capsular polysaccharide. The sialic acid ethyl thioglycoside donor, bearing a 4‐nitropicoloyl moiety as the stereodirecting group at the C4 position, can successfully achieve highly α‐sialylation with various acceptors. The method has been extended to the stereocontrolled synthesis of the protected trisaccharide found in the repeating unit of serotype Ia Group B Streptococcus capsular polysaccharide.