TRIM5α restricts retroviruses in a species-specific manner. Cyclophilin A was independently retrotransposed into the TRIM5loci in different species, leading to the generation of antiviral TRIM5-cyclophilin A (TRIMCyp) proteins. Previously, we foundthat assam macaques express a TRIMCyp chimera (amTRIMCyp), along with a TRIM5α allelic protein (amTRIM5α). Herein,we investigated the antiviral activity of amTRIMCyp and amTRIM5α individually, as well as their interaction and joint effects.amTRIMCyp showed a divergent restriction pattern from amTRIM5α. Although both proteins potently restricted the replicationof HIV-1, only amTRIM5α inhibited N-MLV. Remarkably, cellular anti-HIV-1 activity increased when amTRIMCyp andamTRIM5α were coexpressed, indicating a synergistic block of HIV-1 replication. Consistently, PMBCs from heterozygousamTRIM5α/TRIMCyp showed stronger resistance to HIV-1 infection than those from amTRIM5α/TRIM5α homozygotes. Theanti-HIV-1 synergistic effect was dependent on the amTRIMCyp-amTRIM5α interaction. In contrast, amTRIMCyp completelyabrogated the anti-N-MLVactivity mediated by amTRIM5α, showing a dominant-negative effect, indicating that the generationof amTRIMCyp was involved in the trade-off between divergent restriction activities. Our results provide a new paradigm tostudy functional trade-offs mediated by allelic proteins, a theoretical basis for utilizing animal models with various TRIM5alleles, as well as novel HIV-1 gene therapy strategies.