Ultraviolet radiation stimulates local and systemic immunomodulatory effects in a wavelength-dependant manner. Narrowband UVB (NBUVB) phototherapy is a common and effective treatment for inflammatory skin diseases including psoriasis, but its mechanism of action is not fully understood. This study aims to characterise local and systemic changes in mice following NBUVB irradiation. In a model of contact hypersensitivity, a single exposure to 3 J/cm2 NBUVB suppressed the response to an irritant applied at an unirradiated site. Like exposure to solar simulated UV (ssUV), this immune suppressive dose of NBUVB resulted in Langerhans cell depletion and dermal neutrophil infiltration. Mast cells are a key mediator of ssUV-induced immune suppression, but dermal mast cell frequency was not altered by single or repeated exposure to NBUVB. NBUVB irradiation also generated fewer changes in both the plasma lipidome and lymphocyte recirculation compared to ssUV. However, NBUVB suppressed antigen-specific T cell cytolytic activity in vivo. NBUVB is a potent local immunomodulator that appears to suppress systemic immunity through different mechanisms to ssUV. Understanding the immunomodulatory effects of NBUVB will help identify the forms of phototherapy most likely to be effective for treating a wider range of diseases.