This is a process article for weaving indigenous and mainstream knowledges within science educational curricula and other science arenas, assuming participants include recognized holders of traditional ecological knowledge (we prefer "Indigenous Knowledge" or "Traditional Knowledge") and others with expertise in mainstream science. It is based on the "Integrative Science" undergraduate program created at Cape Breton University to bring together indigenous and mainstream sciences and ways of knowing, as well as related Integrative Science endeavors in science research, application, and outreach. A brief historical outline for that experiential journey is provided and eight "Lessons Learned" listed. The first, namely "acknowledge that we need each other and must engage in a co-learning journey" is explained as key for the success of weaving efforts. The second, namely "be guided by Two-Eyed Seeing" is considered the most profound because it is central to the whole of a co-learning journey and the article's discussion is focussed through it. The eighth lesson, "develop an advisory council of willing, knowledgeable stakeholders" is considered critical for sustaining success over the long-term given that institutional and community politics profoundly influence the resourcing and recruitment of any academic program and thus can help foster success, or sabotage it. The scope of relevance for Two-Eyed Seeing is broad and its uptake across Canada is sketched; the article also places it in the context of emerging theory for transdisciplinary research. The article concludes with thoughts on why "Two-Eyed Seeing" may seem to be desired or resisted as a label in different settings. "Traditional Indian education is an expression of environmental education par excellence." It is an environmental education process that can have a profound meaning for the kind of modern education required to face the challenges of living in the world of the twenty-first century (Cajete (2010), p. 1128, emphasis as in original). As two-eyed seeing implies, people familiar with both knowledge systems can uniquely combine the two in various ways to meet a challenge or task at hand. In the context of environmental crises alone, a combination of both seems essential (Aikenhead and Michell (2011), p. 114).