UNWTO said "strong and coordinated political action" would be vital to opening up destinations in time for the peak summer season.
It follows an 85% slump in tourist arrivals across the continent last year owing to the coronavirus crisis.
"Europe can set a global example by restarting the sector," said the UNWTO.
"Given tourism’s huge socio-economic importance, the benefits that will accompany the return of tourism in time for the peak European season will be felt well outside of the sector itself."
It follows a recent EU delegation to the UNWTO, during which secretary general Zurab Pololikashvili reiterated the importance of common protocols and digital solutions to ensure the safety of international travel.
UNWTO has welcomed the European Commission’s work on the bloc’s digital green pass, which is expected to allow member states to verify visitors Covid status through vaccine certification and Covid test results.
Additionally, it said the commission’s efforts to support individual member states’ recoveries through resilience plans, and the launch of the Re-Open EU website and app, complemented the UNWTO’s #RestartTourism campaign.
"Across Europe, millions of people and businesses are depending on the right decisions to be made so that tourism can restart," said Pololikashvili.
"Now more than ever, tourism needs strong political support and joined-up action. Harmonised travel and health rules are essential to restore confidence and restart tourism."
European Commission vice-president Margaritis Schinas added: “With vaccinations and better management of the crisis, there is no doubt this summer will be better than last. Reopening borders will have an impact beyond tourism. It will drive Europe’s overall recovery.
"Europe will not return on its own. Europe is part of the world and we are ready find a way that the European green pass works with solutions provided by countries or groups of countries from outside the EU."
