Travel and tourism are essential to global economies, generating social, economic, and environmental impacts. However, there is a lack of standardized methodologies to assess the environmental footprint of tourist destinations beyond carbon footprint analysis. This study introduces the Greentour tool, the first of its kind to evaluate the environmental impact of accommodation, restaurants, and tourism activities using nine environmental indicators from a life cycle assessment (LCA) perspective. The tool applies a hybrid bottom-up and top-down approach, integrating data from tourist establishments and destination managers. The tool was tested in four tourist destinations in Spain and Portugal (Rías Baixas, Camino Lebaniego, Lloret de Mar, and Guimarães), revealing that transportation is the primary contributor to environmental impacts, ranging from 60% to 96% of total emissions, particularly in air-travel-dependent destinations. Food and beverage services are the second-largest contributor, accounting for up to 26% of emissions, while accommodation ranks third (1–14%). This study highlights the significant role of electricity consumption and food choices (e.g., red meat and dairy) in greenhouse gas (GHG) emissions, emphasizing the need for sustainable alternatives. Despite challenges in data collection, particularly for food and transport statistics, the Greentour tool has demonstrated robustness and adaptability across diverse destinations, making it applicable worldwide. This tool provides key insights for policymakers, tourism stakeholders, and businesses, supporting the integration of sustainability strategies into public policies and industry best practices. Future research should focus on expanding its use to additional destinations to foster science-based decision-making and promote more sustainable tourism practices globally.