This study was aimed to evaluate the growth performance and gonadal development of diploid and triploid striped catfish Pangasianodon hypophthalmus. Triploids were produced through a heat shock method at 42 °C for two minutes, at two minutes after fertilization. Before treatment performed, group of triploid and diploid were separated through nucleolus counting confirmed cromoseme counting. Five individual of each group at the age of nine months were tagged and reared for two months. Parameter of growth performance, feed conversion ratio, and survival rate were analysed using independent-samples t-test at confidence interval 95%, while gonadosomatic index (GSI) and gonad histology were analysed descriptively. No significant differences were observed between diploid and triploid fish in terms of growth performance, feed conversion ratio, and survival rate (P>0.05) during the two months rearing period, while GSI was higher in diploid (P0,05). Nilai GSI diploid lebih tinggi (P<0,05) dibandingkan triploid, baik pada jantan maupun betina. Hasil histologi menunjukkan bahwa gonad ikan patin betina masih pada tahap perkembangan awal. Namun, indikasi steril terlihat dengan adanya degradasi oosit dan perkembangannya yang terganggu. Gonad jantan berkembang lebih cepat dibandingkan betina, dengan ditemukannya spermatid pada beberapa lobule. Gonad jantan triploid menunjukkan adanya gejala sterilitas tetapi tidak permanen, sebagian masih mampu berkembang hingga fase spermatid, namun jumlahnya lebih sedikit dibandingkan diploid. Berdasarkan penelitian, disimpulkan bahwa pertumbuhan antara ikan patin siam diploid dan triploid hingga umur 11 bulan tidak menunjukkan perbedaan, akan tetapi gejala sterilitas ditemukan baik pada jantan maupun betina triploid. Kata kunci: diploid, triploid, pertumbuhan, gonad, Pangasianodon hypophthalmus