The present study was designed to evaluate the physiological-insecticidal activity of triflumuron as IGI on amino acids content in the testes and ovaries of both sexes reproductive tracts of Spodoptera littoralis. The lethal dose 50% of those individuals subjected to triflumuron (LD₅₀=0.006 μl/larva) was topically applied on newly molted fifth instar larvae of the cotton leafworm S. littoralis. The treatment decreased the amounts of amino acids content of testes of adult males (2 days-old) obtained from treated larvae. This content was highly noticed and were ranged between 0.00 to 9.65% in 9 amino acids from 16 total amino acids examined i.e.  DL-2-Amino-N-butyric Acid, Tryptophan(TRP), Isoleucine(ILE), DL-Threonine(THR), L-Arginine(ARG), L- Leucine(LEU), L- Alanine(ALA), DL- Serine(SER) and L- Lysine(LYS), while these amino acids amount percentages were ranged between 3.45 to 16.94%. The present results showed strong effects of LD₅₀ of triflumuron on the major amino acids that may stimulate and activate certain physiological functions in spermatogenesis in the testes of male reproductive tract i.e. SER and LYS. These latter amino acids in control males (2days-old) were 5.51 and 3.45%, respectively, but they were zero% in treated males.  Both amino acids SER and LYS may play many important roles in the structure of both types of spermatozoa of the cotton leafworm. Moreover, the greatest decrease in amino acid content was observed especially in case of LYS (zero %) with triflumuron (LD₅₀) , while it was 19.92% in control female. LYS may play a specific role in the structure of egg of the cotton leafworm. The greatest increase of amino acid content was noticed in case of ASPARTIC ACID (ASP) (17.40%) with triflumuron (LD₅₀), while it was zero% in control female. The average weight of ovaries andtesticles were recorded (32.21, 1.08 mg) with treated female and male by triflumuron in respect, while it was 78.65, 3.74 mg in control female and male, respectively. The results indicated that the biochemical composition of both sexes reproductive tracts were reduced. Triflumuron caused reproductive suppression, also, it affects the amino acids amount and it had its function on adults reproductive tracts, ultimately leading to reduce sperm transfer from the treated male insect to female.