Exposure to ultraviolet (UV) radiation leads to a progressive increase in dermal damage through the degradation of collagen, which is mediated by matrix metalloproteinases (MMPs). UV radiation alters the intracellular signaling events that regulate the elaboration of MMPs. Our previous study showed that P165, the N-terminal 5-mer peptide analog of amyloid precursor protein, exerts a protective effect on ultraviolet A (UVA)-induced loss of collagen type I in human dermal fibroblasts (HDFs) by inhibiting the generation of intracellular reactive oxygen species and MMP-1. In this study, we focused on specific signal transduction pathways to elucidate the possible photoprotective mechanisms of P165 in controlling MMP-1 inhibition. Results from western blot analyses indicated that pretreatment with P165 dose-dependently inhibited UVA-induced phosphorylation of extracellular regulated protein kinases (ERK), c-Jun N-terminal kniase (JNK), p38 mitogen-activated protein kinases (MAPKs), and the phosphorylation of their downstream targets c-Jun and c-Fos. The photoprotective effects of P165 were further demonstrated in collagen type I secretion and cellular senescence induced by UVA irradiation. These findings suggest that P165 exerts photoprotective activity in UVA-treated HDFs by regulating MMP-1 generation. This activity may be mediated by inhibiting the MAPK signaling pathways. Thus, P165 is a potential agent for the prevention of skin photoaging.