Tourism is often considered the world’s biggest industry, as it contributes approximately 10% of the global GDP. Despite this economic impact, tourism also includes important critical issues like territorial inequalities, diminishment of local engagement, and has high environmental and cultural impacts. This study investigates the rise of “walking trail tourism”, a niche sector where the respect for local communities and the environmental sustainability are particularly important. The focus is on Italy and Argentina: two countries with very different political, tourism, and biophysical backgrounds, but with the common recent development of walking trails and forms of social innovation. This study explores three main questions: the trends in walking trail tourism, the role of these trails in fostering local social innovation, and the influence of national policies in this domain. The study combines historical-statistical analysis, political–legislative review, and interviews with experts in order to assess all these aspects. Findings reveal significant social innovation trends within walking trail tourism but also challenges in territorial coordination and the establishment of national governance. Italy and Argentina are both characterized by an opposite situation regarding walking trails: there are several local initiatives but a lack of national guidelines in the former, and some good national policies but few bottom-up initiatives in the latter.