Advanced practice providers (APPs) are essential members of intensive care unit (ICU) interprofessional teams and are expected to be competent in performing procedures. There are no published criteria for establishing when APPs can independently perform procedures. Simulation-based mastery learning (SBML) is an effective strategy for improving critical care skills but has not been applied to practicing ICU APPs. The purpose of this study was to evaluate if an SBML curriculum could improve the critical care skills and procedural self-confidence of ICU APPs. We performed a pretest-posttest study of central venous catheter (CVC) insertion, thoracentesis, and mechanical ventilation (MV) management skills among ICU APPs who participated in an SBML course at an academic hospital. For each skill, APPs underwent baseline skills assessments (pretests) on a simulator using previously published checklists, followed by didactic sessions and deliberate practice with individualized feedback. Within 2 weeks, participants were required to meet or exceed previously established minimum passing standards (MPS) on simulated skills assessments (posttests) using the same checklists. Further deliberate practice was provided for those unable to meet the MPS until they retested and met this standard. We compared pretest to posttest skills checklist scores and procedural confidence. All 12 eligible ICU APPs participated in internal jugular CVC, subclavian CVC, and MV training. Five APPs participated in thoracentesis training. At baseline, no APPs met the MPS on all skills. At training completion, all APPs achieved the mastery standard. Internal jugular CVC pretest performance improved from a mean of 67.2% (standard deviation [SD], 28.8%) items correct to 97.1% (SD, 3.8%) at posttest (P = 0.005). Subclavian CVC pretest performance improved from 29.2% (SD, 32.7%) items correct to 93.1% (SD 3.9%) at posttest (P < 0.001). Thoracentesis pretest skill improved from 63.9% (SD, 30.6%) items correct to 99.2% (SD, 1.7%) at posttest (P = 0.054). Pretest MV skills improved from 54.8% (SD, 19.7%) items correct to 92.3% (SD, 5.0%) at posttest (P < 0.001). APP procedural confidence improved for each skill from pre to posttest. SBML is effective for training APPs to perform ICU skills. Relying on traditional educational methods does not reliably ensure that APPs are adequately prepared to perform skills such as CVC insertion, thoracentesis, and MV management.