Serine-arginine-rich splicing factors (SRSFs) are members of RNA processing proteins in the serine-arginine-rich (SR) family that could regulate the alternative splicing of the human immunodeficiency virus-1 (HIV-1). Whether SRSF9 has any effect on HIV-1 regulation requires elucidation. Here, we report for the first time the effects and mechanisms of SRSF9 on HIV-1 regulation. The overexpression of SRSF9 inhibits viral production and infectivity in both HEK293T and MT-4 cells. Deletion analysis of SRSF9 determined that the RNA regulation motif domain of SRSF9 is important for anti-HIV-1 effects. Furthermore, overexpression of SRSF9 increases multiple spliced forms of viral mRNA, such as Vpr mRNA. These data suggest that SRSF9 overexpression inhibits HIV-1 production by inducing the imbalanced HIV-1 mRNA splicing that could be exploited further for a novel HIV-1 therapeutic molecule. [BMB Reports 2022; 55(12): 639-644].