A convenient approach has been presented for the synthesis of N^β-protected amino diselenides from the corresponding amino alkyl iodides using in situ generated NaBH₂Se₃ as an efficient selenating reagent. All the diselenides are obtained in good yields under very mild conditions, short duration times and the protocol is free from racemization. The methodology has been effectively extended to the synthesis of N-protected L-selenocystine methyl ester. Clean oxidation of N^β-protected amino diselenides to N^β-protected amino seleninic acids using 35% aqueous H₂O₂ has also been accomplished. The present protocol is compatible with all the common urethane protecting groups.