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Nonablative lasers are used for dermal collagen remodeling. Although clinical improvements have been reported using various laser devices, the mechanism of dermal collagen remodeling remains unknown.To investigate the effects of energy fluences of the long-pulsed neodymium-doped yttrium aluminum garnet (Nd:YAG) nonablative laser on dermal collagen remodeling and evaluate the dermal collagen remodeling mechanism.Hairless mice were pretreated with ultraviolet B irradiation to produce photo-damage. The laser treatment used a long-pulse 1,064-nm Nd:YAG laser at energy fluences of 20, 40, and 60 J/cm2. The amount of dermal collagen and expressions of transforming growth factor beta (TGF-β), matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1) of laser treated skin were compared with those of nontreated control skin.The long-pulse Nd:YAG laser treatment increased dermal collagen and significantly increased TGF-β expression. The expression of MMP-1 decreased with low energy fluence. The expression of TIMP-1was not significantly different.Long-pulsed 1,064-nm Nd:YAG laser increases the dermal collagen in association with the increased expression of TGF-β.