The UVB component of the sunlight (290-320 nm) plays an important role in carcinogenesis through generation of high levels of bipyrimidine DNA photoproducts, while UVA (320-400 nm) has been associated with photoaging and tumor progression through generation of low, but continuous levels of DNA damage and oxidative stress. However, the contribution of UVA light to epidermal cell fate in the context of photoaging remains poorly understood. Here, by using proteomic analyses and biochemical assays for validation, we show that UVA induces proteome remodeling and senescence in primary keratinocytes, eliciting potent antioxidant and pro-inflammatory responses. As a model of early skin tumorigenesis during aging, immortalized non-malignant keratinocytes, bearing potentially oncogenic mutations and dysfunctional components of the senescent machinery , are resilient to UVA-induced stress, but are sensitive to paracrine oxidative stress and immune system activation induced by senescent neighboring keratinocytes. These observations reveal a new cellular mechanism by which UVA induces photoaging in the epidermis.