Salt intake in adults and children exceeds recommended levels. Salt-related knowledge, attitudes, and behaviours (KABs) may influence the amount of salt consumed. The aims of this study were to assess salt-related KABs among parents, and investigate whether salt-related knowledge and attitudes are associated with salt-specific behaviours. Parents with children <18 years were recruited from four shopping centers across Victoria, Australia; Facebook; and an online consumer research panel; they then completed an online questionnaire assessing salt-related KABs and salt use in children. Eight hundred and thirty-seven parents (mean age 41.0 (10.0) (SD) years) provided valid responses. Most (77%) parents were aware that eating too much salt damages children’s health and that reducing the amount of salt in their children’s diet was important (70%), and 46% reported adding salt to food prepared for their children. Parents who were aware that eating too much salt damages children’s health were less likely to report that their child added salt at the table (OR = 0.51, p < 0.001), and that they added salt to food prepared for the child (OR = 0.46, p < 0.001). Educational messages that highlight the adverse health effects of salt during childhood are likely to be useful in reducing discretionary salt use in the home environment.