[Objectives]  The cotton bollworm, Helicoverpa armigera, is one of the most serious pests of cotton, corn and many other crops in China. Although high reproduction is the basis for outbreaks of this pest, information on reproduction- related genes of this species is lacking. [Methods]  We sequenced ovary and testis transcriptomes of H. armigera on an Illumina HiSeq2500 platform and identified numerous genes that may be involved in gonadal development, gametogenesis and reproduction. [Results]  Raw reads were assembled into 100 603 unigenes with a mean length of 666.05 bp and an N50 of 1 114 bp. A similarity search resulted in 52 071 unigenes being annotated, most of which with reference to the Nr database. Gene expression in the ovary and testis were then compared, and 7 714 differentially expressed genes (DEGs) were identified. Among these genes, 3 288 were up-regulated in the ovary and 4 426 were up-regulated in the testis. Based on KEGG enrichment analyses, the pathways involved in the regulation of gonadal development and gametogenesis were identified, including the “mTOR signaling”, the “Oocyte meiosis”, “Insulin signaling” and “GnRH signaling”, pathways. To further screen the transcriptome database, numerous DEGs involved in gonadal development and gametogenesis were identified, including vitellogenin (Vg), vitellogenin receptor (VgR), chorion-related genes, testis-specific serine/threonine- protein kinase and spermatogenesis-associated protein. Finally, twelve DEGs were selected for RT-qPCR analysis, the expression patterns of which were consistent with the results obtained from transcriptome sequencing. [Conclusion]  This study acquired the transcriptome data and identified a series of genes related to gonadal development, providing a basis for exploring the mechanisms regulating reproduction in H. armigera.