Stream bank erosion in agricultural landscapes is one of the major pathways of non-point source sediment and phosphorus to streams. The aim of this research was to quantify and compare sediment and total phosphorus losses from stream bank erosion among grazed pastures that were managed under different stocking densities and identify factors that influence different patterns of stream bank erosion. Stream bank erosion rates over two years were calculated by using the erosion pin method. Eroded stream bank length, height and soil bulk density and total stream bank soil-P concentrations were also measured to calculate total soil and P lost via stream bank erosion. Soil and total P lost from stream bank erosion did not reveal any significant correlations with stocking density per stream length ranging from 0.23 to 1.15 (cow calf pairs ha-1 * days yr‾¹)/ (m) suggesting that all densities had similar impacts. On the other hand, highly correlated relationships were found between the annual precipitation amounts and erosion rates (p= 0.0003; R2 = 0.86) suggesting that precipitation is one of the major factors driving stream bank erosion. Frequency, intensity and timing of precipitation events during May to August can be a major factor promoting stream bank collapse and soil loss. Stream bank soil bulk density and texture also had a significant influence on soil loss (p= 0.0138; R2 = 0.60). Stream bank with lower soil bulk densities had higher stream bank soil losses than stream banks with higher soil bulk densities. Since riparian pastures are highly attractive to livestock it is difficult to manage them without some impact on the stream bank erosion unless some method of livestock exclusion from the channel is used.