Streamflow is an important means of nutrient export off most watersheds. In agricultural areas, effluent from artificial drainage can be an important contribution to streamflow nutrient loads. The objective of this study was to examine seasonal variations of nutrients in streamflow and to quantify the effects of artificial drainage effluent on streamflow nutrients on an agricultural watershed. Concentrations and loads of NO3-N, NH4-N, organic N, dissolved molybdate-reactive P, total P, Ca, Mg, K, Cl, and SO4-S were measured in streamflow and artificial drainflow on a 1568-ha agricultural watershed near Tifton, Ga. All 10 streamflow sampling sites had maximum NO3-N and SO4-S concentrations in winter and most reached minima during summer. Concentrations of NO3-N, Ca, Mg, K, and Cl were generally much higher in drainage water than streamflow. Load of NO3-N from drained row-cropped fields was about 40.4 kg ha−1 y−1, 60 times the per-hectare NO3-N load from the mixed cover watershed. Loads of organic N, Ca, Mg, K, SO4-S, and Cl from the mixed cover watershed were 2.8, 9.3, 4.5, 6.5, 17.0, and 30.0 kg ha−1 y−1, respectively. Loads (per hectare) of organic N were lower from the drained fields, but loads of Ca, Mg, K, SO4-S, and Cl were lower from the mixed cover watershed. In-stream and riparian zone processes apparently converted inorganic N to organic forms and removed N through denitrification. Annual streamflow N load was about 29% of the precipitation input of 12.2 kg ha−1 y−1. Sediment-associated N and P loads in streamflow were 0.35 and 0.09 kg ha−1 y−1, respectively, accounting for 9.0 and 8.5% of total N and P, respectively. The two highest flow events for the year carried 19% of the total annual flow and 19% of the annual sediment load, but had 30 and 27% of the total annual sediment N and P loads, respectively. This enrichment of sediment-associated N and P indicates that part of this sediment load moved directly from upland areas.