IMPORTANCE: Intensive care unit (ICU) telemedicine (TM) programs have been promoted as improving access to intensive care specialists and ultimately improving patient outcomes, but data on effectiveness are limited and conflicting. OBJECTIVE: To examine the impact of ICU TM on mortality rates and length of stay (LOS) in an integrated health care system. DESIGN, SETTING, AND PARTICIPANTS: Observational pre-post study of patients treated in 8 "intervention" ICUs (7 hospitals within the US Department of Veterans Affairs health care system) during 2011-2012 that implemented TM monitoring during the post-TM period as well as patients treated in concurrent control ICUs that did not implement an ICU TM program. INTERVENTION: Implementation of ICU TM monitoring. MAIN OUTCOMES AND MEASURES: Unadjusted and risk-adjusted ICU, in-hospital, and 30-day mortality rates and ICU and hospital LOS for patients who did or did not receive treatment in ICUs equipped with TM monitoring. RESULTS: Our study included 3355 patients treated in our intervention ICUs (1708 in the pre-TM period and 1647 in the post-TM period) and 3584 treated in the control ICUs during the same period. Patient demographics and comorbid illnesses were similar in the intervention and control ICUs during the pre-TM and post-TM periods; however, predicted ICU mortality rates were modestly lower for admissions to the intervention ICUs compared with control ICUs in both the pre-TM (3.0%vs 3.6%; P = .02) and post-TM (2.8%vs 3.5%; P < .001) periods. Implementation of ICU TM was not associated with a significant decline in ICU, in-hospital, or 30-day mortality rates or LOS in unadjusted or adjusted analyses. For example, unadjusted ICU mortality in the pre-TM vs post-TM periods were 2.9% vs 2.8% (P = .89) for the intervention ICUs and 4.0% vs 3.4%(P = .31) for the control ICUs. Unadjusted 30-day mortality during the pre-TM vs post-TM periods were 7.7%vs 7.8% (P = .91) for the intervention ICUs and 12.0% vs 10.2%(P = .08) for the control ICUs. Evaluation of interaction terms comparing the magnitude of mortality rate change during the pre-TM and post-TM periods in the intervention and control ICUs failed to demonstrate a significant reduction in mortality rates or LOS. CONCLUSIONS AND RELEVANCE: We found no evidence that the implementation of ICU TM significantly reduced mortality rates or LOS.