The Integrator complex plays a crucial role in the termination of RNA polymerase II (Pol II) transcription at promoter-proximal regions. Previous studies have elucidated how Integrator binds to the paused elongation complex (PEC) formed by Pol II, DSIF, and NELF and cleaves the nascent RNA transcript, but the mechanism by which Integrator removes Pol II from the DNA template remains unclear. This study presents three cryo-electron microscopy (cryo-EM) structures of the complete Integrator-PP2A complex in different functional states. The pre-termination complex structure reveals a previously unresolved scorpion-tail-shaped INTS10–INTS13–INTS14–INTS15 module that may use its 'sting' to open the DSIF DNA clamp and facilitate termination. The post-termination complex structure shows that the INTS3 subunit and associated SOSS factors prevent Pol II reassociation with Integrator after termination. The free Integrator-PP2A complex structure in an inactive closed conformation reveals that INTS6 blocks the PP2A phosphatase active site. These structures provide insights into how Integrator terminates Pol II transcription in three steps involving major rearrangements. The first step involves the dephosphorylation of the Pol II CTD by PP2A, counteracting the kinase activity of P-TEFb. The second step involves the displacement of the DSIF DNA clamp and upstream DNA by the tail module, followed by the cleavage and degradation of the nascent RNA transcript. The third step involves the release of the DNA from the Pol II cleft, facilitated by the INTS13–INTS14 module. The INTS3 subunit and associated SOSS factors prevent Pol II reassociation with Integrator by binding to the INTS7 surface. The INTS6 inhibitory loop blocks the PP2A-C active site, ensuring that the phosphatase is inactive in the free Integrator-PP2A complex. This model of Integrator-dependent Pol II termination is conceptually similar to current models of Pol II termination by other factors, such as the torpedo model involving the 5′–3′ exonuclease XRN2.The Integrator complex plays a crucial role in the termination of RNA polymerase II (Pol II) transcription at promoter-proximal regions. Previous studies have elucidated how Integrator binds to the paused elongation complex (PEC) formed by Pol II, DSIF, and NELF and cleaves the nascent RNA transcript, but the mechanism by which Integrator removes Pol II from the DNA template remains unclear. This study presents three cryo-electron microscopy (cryo-EM) structures of the complete Integrator-PP2A complex in different functional states. The pre-termination complex structure reveals a previously unresolved scorpion-tail-shaped INTS10–INTS13–INTS14–INTS15 module that may use its 'sting' to open the DSIF DNA clamp and facilitate termination. The post-termination complex structure shows that the INTS3 subunit and associated SOSS factors prevent Pol II reassociation with Integrator after termination. The free Integrator-PP2A complex structure in an inactive closed conformation reveals that INTS6 blocks the PP2A phosphatase active site. These structures provide insights into how Integrator terminates Pol II transcription in three steps involving major rearrangements. The first step involves the dephosphorylation of the Pol II CTD by PP2A, counteracting the kinase activity of P-TEFb. The second step involves the displacement of the DSIF DNA clamp and upstream DNA by the tail module, followed by the cleavage and degradation of the nascent RNA transcript. The third step involves the release of the DNA from the Pol II cleft, facilitated by the INTS13–INTS14 module. The INTS3 subunit and associated SOSS factors prevent Pol II reassociation with Integrator by binding to the INTS7 surface. The INTS6 inhibitory loop blocks the PP2A-C active site, ensuring that the phosphatase is inactive in the free Integrator-PP2A complex. This model of Integrator-dependent Pol II termination is conceptually similar to current models of Pol II termination by other factors, such as the torpedo model involving the 5′–3′ exonuclease XRN2.