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The occurrence patterns and molecular characteristics of Salmonella are important for surveillance and control of the pathogens. Objectives of this study were to determine month-to-month variation and seasonal effects on the occurrence of Salmonella in dairy animals and environments and to characterize selected Salmonella isolates. A total of 7680 animal and environmental samples, collected monthly from a dairy farm, were analyzed for the presence of Salmonella during a 12-month study. Major sources of Salmonella on the dairy farm (% positive) were milking parlor air (62%) and bird droppings (63%) during winter; feeds (50–58%), water (53–67%), calf bedding (63%), soils (60–63%), milking parlor air (60%), and bird droppings (50%) in spring; all animal and environmental samples (40–92%) except milking parlor air (25%) and bulk tank milk (29%) in summer; and feeds (60–71%), cow beddings (59%), cow soils (50%), air (46–71%), and insects (63%) during fall. Salmonella ribotyping indicated that most serovars came from different sources but some might have originated from a common source and transmitted from site to site on the farm. These data provide some important information on key animal and environmental sampling sites needed to initiate on-farm management programs for control of this important foodborne pathogen.