Atmospheric nitrogen (N) deposition has the potential to alter plant tissue chemistry. Increased N inputs cause an increase in foliar N; however, the effect of N inputs on foliar phosphorus (P) has been understudied, especially in semi-arid coastal sage scrub (CSS) and chaparral shrublands of southern California. We used archived leaf samples from dominant semi-deciduous CSS (Artemisia californica and Salvia mellifera) and evergreen chaparral (Adenostoma fasciculatum and Ceanothus greggii) shrubs to assess the effects of long-term (17 years) experimental N enrichment on leaf N and P concentrations and the N:P ratio. We hypothesized that long-term N addition would cause a decrease in the leaf P concentration due to growth dilution and an increase in the N:P ratio. We found that N addition caused a rapid and significant increase in leaf N concentration but no change in P, suggesting that P uptake was keeping up with demand. We also found a positive relationship between foliar P concentrations and annual precipitation of all shrubs except C. greggii. These results indicate that long-term N enrichment raised foliar N concentration in these semi-arid shrublands but had no effect on foliar P and that water availability affected interannual variations in foliar P more than N exposure.