Secondary ice production (SIP) is the generation of ice particles from pre-existing ice particles in clouds. SIP contrasts with primary ice production, i.e. ice nucleation. While ice nucleation remains poorly understood, even less is known about SIP, and few climate models represent one or more SIP mechanisms. We implemented the three SIP mechanisms into the CESM2 model: (i) droplet shattering during rain freezing and (ii) ice-ice fragmentation in addition to the (iii) Hallett-Mossop rime splintering process that is included in the standard version of the model and evaluate its influence on Earth’s present and future climate. We find that the inclusion of SIP processes decreases the climate sensitivity of the CESM2 model by ~0.7˚C and is largely driven by an expected strengthening of the cloud-phase feedback whereby an increased mass and number concentration of ice crystals is replaced by liquid droplets, and operates predominantly in Earth’s extratropical latitudes. We also identify a contrasting state-dependent tropical microphysics-dynamics coupled response in the tropics that further dampens the Walker circulation in a perturbed warmed state. This response is driven by SIP-induced weakened updrafts in the Tropical West Pacific and weakened downdrafts in the Tropical East Pacific by altering the vertical distribution of diabatic heating. In the west, SIP enhances melting-layer cooling and depositional heating aloft, whereas in the east it increases upper-tropospheric sublimative cooling through a greater concentration of suspended ice particles and enhances lower-tropospheric warming by reducing ice sedimentation. Together, these changes modify the tropical heating gradient and further dampen the Walker circulation in a warmer climate. Our results emphasize the need for global observational constraints on SIP and its implementation into climate models used to inform climate policy.