Combine walnuts and maple syrup in a large bowl; mix until evenly coated. Stir in sesame seeds.
Spread on non-stick, or parchment paper-lined baking sheet. Baked at 325°F [160°C] for 25 minutes, stirring twice, until walnuts are lightly browned. Cool on baking sheet; walnuts will become dry and crunchy as they cool. Store in airtight container in refrigerator.