Bring sprouts, 1/2 cup water, and 1/2 teaspoon salt to boil in 2-quart saucepan over medium-high heat. Lower heat, cover, and simmer (shaking pan once or twice to redistribute sprouts) until knife tip inserted into a brussels sprout center meets no resistance, 8 to 10 minutes. Drain well and set aside.
Heat oil in large skillet over medium heat. Add nuts; cook, stirring frequently, until nuts begin to brown, about 2 minutes. Add garlic; cook until softened, about 1 minute.
Stir in sprouts and cook, stirring constantly, until heated through, 2 to 3 minutes. Season to taste with salt and pepper and serve.