Governments have attempted to increase clinical trial activity in their jurisdictions using a range of methods including simplifying the ethics review and governance process of clinical trials. This study’s objective was to systematically review the effects of government actions targeting ethics reviews or governance processes on clinical trial activity. The data sources of Pub Med, Scopus, Sage, ProQuest, Google, Google Scholar and reference lists were all searched between 9/8/20 and 6/9/20. From these sources, 1455 potentially eligible reports were reviewed and full text assessments were done for 295. Thirty-eight reports provided data on 45 interventions—13 targeting ethics review and 32 targeting governance processes—were included. There were data describing effects on a primary or secondary outcome (the number of clinical trials or expenditure on clinical trials) for 39/45 of the interventions. 23/39 (59%) reported positive effects, meaning a greater number of trials and/or expenditure on clinical trials (6/11 ethics, 17/28 governance), 7/39 (18%) reported null effects (4/11 ethics, 3/28 governance) and 9/39 (23%) reported adverse effects (1/13 ethics, 8/28 governance). Positive effects were attributable to interventions that better defined the scope of review, placed clear expectations on timelines or sought to achieve mutual acceptance of ethics review outcomes. Adverse effects were mostly caused by governance interventions that unintentionally added an extra layer of bureaucracy or were developed without full consideration of the broader clinical trial approval system. Governments have an opportunity to enhance clinical trial activity with interventions targeting ethics reviews and governance processes but must be aware that some interventions can have an adverse impact.