The impact of ultrasound pretreatment of p-aramide fibers is investigated to reduce negative effects of fiber aging induced by artificial white light (Suntest), as well as by sunlight and weathering. The investigations indicate that such a pretreatment has a beneficial influence in reducing the aging tendency of the fibers. The ultrasound pretreatment reduces strength losses due to aging in a natural environment by up to 40%, and as much as 60% in artificial environment. A positive impact of the duration of ultrasound treatments is also established in assessing the resistance of p-aramide fibers to aging.