The probiotic Lactobacillus rhamnosus HN001 is known to enhance immunity in animal models, following oral delivery. In this study, we investigated the immunoenhancing effects of HN001 delivered to mice in different milk-based substrates, including: whole (full-fat) milk supplemented with HN001; fermented milk supplemented with HN001; or whole milk which had been part-fermented by HN001. Direct oral feeding of mice with HN001 in whole milk was shown to enhance the phagocytic activity of blood and peritoneal cells. Similar effects on phagocytosis were observed when HN001 was offered to mice in the form of a milk- or fermented milk-based diet. The degree of immune enhancement conferred by HN001 was similar whether the probiotic was used as an additive or as a fermentative agent. These studies confirm that Lb. rhamnosus HN001, derived originally from dairy food, enhances immune function following oral delivery in different milk bases.