Background Acne treatments using laser and light devices have been reported to have varying degrees of efficacy. However, there has been no study of treatment of acne using a dual mode (quasi-long pulse and Q-switched mode) 1064-nm Nd:YAG laser assisted with a topically applied carbon suspension. Objective To evaluate the clinical efficacy, safety, and histological changes of new laser treatment method for acne vulgaris. Methods Twenty-two patients received 3 sessions of quasi-long pulse and Q-switched Nd:YAG laser treatment assisted with a topically applied carbon suspension at 2-week intervals in a randomized split face manner. Results At the final visit, the inflammatory acne lesions were reduced on the laser-treated side by 58.6% (P < .001), but increased on the untreated side by 5%. The noninflammatory acne lesions were reduced on the laser-treated side by 52.4% (P < .001). Sebum output reduction, inflammatory cell and cytokine reductions, a decrease of the thickness of a perifollicular stratum corneum and a full epithelium, and skin rejuvenation effect were found. The histopathologic examination of the acne lesions showed decreased inflammation and immunostaining intensity for interleukin 8, matrix metalloproteinase-9, toll-like receptor-2, and nuclear factor kappa B, and tumor necrosis factor alpha was reduced significantly. No severe adverse reactions were reported. All patients reported mild transient erythema that disappeared in a few hours. Limitations The number of subjects studied was small. Conclusions This laser treatment was rapid and effective for treating not only the inflammatory but also the noninflammatory acne lesions when compared with the control side. The histopathologic findings correlated well with the clinical acne grade and treatment response. This novel laser treatment appears to be safe and effective for acne treatment.