Exposure to ionizing radiation during cardiac catheterization can have harmful consequences for patients and for the medical staff involved in the procedures. Minimizing radiation doses during the procedures is essential. We investigated whether fine-tuning the radiation protocol reduces radiation doses in the cardiac catheterization laboratory. In January 2016, we implemented a new protocol with reduced radiation doses in the Hospital de Jerez catheterization laboratory. We analyzed 170 consecutive coronary interventional procedures (85 of which were performed after the new protocol was implemented) and the personal dosimeters of the interventional cardiologists who performed the procedures. Overall, the low-radiation protocol reduced air kerma (dose of radiation) by 44.9% (95% CI, 18.4%–70.8%; P=0.001). The dose-area product decreased by 61% (95% CI, 30.2%–90.1%; P <0.001) during percutaneous coronary interventions. We also found that the annual deep (79%, P=0.026) and shallow (62.2%, P=0.035) radiation doses to which primary operators were exposed decreased significantly under the low-radiation protocol. These dose reductions were achieved without increasing the volume of contrast media, fluoroscopy time, or rates of procedural complications, and without reducing the productivity of the laboratory. Optimizing the radiation safety protocol effectively reduced radiation exposure in patients and operators during cardiac catheterization procedures.