This study aimed to characterize the morphological changes in the ovary of the female crab Neptunus pelagicus and to identify specific fractions of vitelloginin and vitelline molecules during primary and secondary vitellogenesis. Samples of the blue crab were collected from the Mediterranean Sea of Alexandria monthly during 2017. Ovaries and oocytes in primary and secondary vitellogenesis were detached and treated for histological test. Native polyacrylamide gel electrophoresis (PAGE) Bis-Tris Gels was applied to identify vitelloginin (VN) and vitelline (VL) molecules. Protein Analyses were done by PAGE-SDS. The initial degenerate primers were built regarding the conserved amino acid domains of the yolk proteins. Primary and secondary vitellogeneses consisted of 8 phases. Lipoprotein fraction with molecular weight 550 kDa was identified in the hemolymph in secondary vitellogenesis. Two protein fractions (VLⅠ & VLⅡ) were identified in secondary vitellogenic oocytes. The electrophoresis performed with extract of stage Ⅰ oocyte showed two protein fractions with molecular weights 550 kDa and 460 kDa. In stage Ⅱ and Ⅲ oocyte, 4 subunits were presented of 180, 195, 140 and 120 kDa in VLⅠ and 2 subunits with molecular weight of 110 kDa and 95 kDa in VLⅡ. Another two fractions in stage Ⅴ oocyte presented with molecular weights of 380 kDa and 360 kDa. West blot analysis proved that both fractions were of four major polypeptide subunits with molecular weight of 180, 125, 90 and 85 kDa in each of the two VLs. The hybridization signal obtained by the North blot was detected in the hepatopancreas during ovarian cycle and in the ovary during secondary vitellogenesis. The result of the reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the mRNA that encodes the C-terminal region of the VN cDNA was found in the ovary in secondary vitellogenesis and in the hepatopancreas.