Aims To assess impacts of exotic grass invasion on nutrient losses from California coastal sage scrub (CSS), we quantified interactive effects of season, exotic grass litter, and plant cover type on wetting-induced emissions of carbon and nitrogen trace gases from CSS soils. Methods We added grass litter to plots dominated by native Erioginum fasciculatum or exotic Schismus barbatus in invaded California CSS. In both dry and wet seasons, we conducted 48-hour wetting experiments and measured soil emissions of CO2, N2O, and NOx. Results CO2 and N2O pulses appeared 15 minutes post-wetting, diminishing within twelve hours. NOx peaked between 6 to 12 hours, remaining elevated at 48 hours. Dry-season pulses were seven times higher than wet-season pulses. Grass litter amendments increased CO2 and dry-season N2O pulses without significantly altering NOx pulses. Grass cover reduced CO2 pulses compared to shrub cover. Conclusions Our results suggest that CSS soils produce stronger trace gas pulses of CO2, N2O, and NOx during the dry season when wetting is less frequent. Although grass cover potentially constrains soil CO2 respiration, grass litter loading during the dry season may provide carbon-rich substrates that stimulate additional microbial production of CO2 and N2O but not NOx.