Genetic variation in LRRK2 associates with the susceptibility to Parkinson's disease, Crohn's disease, and mycobacteria infection. High expression of LRRK2 and its substrate Rab10 occurs in phagocytic cells in the immune system. In mouse and human primary macrophages, dendritic cells, and microglia‐like cells, we find that Rab10 specifically regulates a specialized form of endocytosis known as macropinocytosis, without affecting phagocytosis or clathrin‐mediated endocytosis. LRRK2 phosphorylates cytoplasmic PI(3,4,5)P3‐positive GTP‐Rab10, before EEA1 and Rab5 recruitment to early macropinosomes occurs. Macropinosome cargo in macrophages includes CCR5, CD11b, and MHCII, and LRRK2‐phosphorylation of Rab10 potently blocks EHBP1L1‐mediated recycling tubules and cargo turnover. EHBP1L1 overexpression competitively inhibits LRRK2‐phosphorylation of Rab10, mimicking the effects of LRRK2 kinase inhibition in promoting cargo recycling. Both Rab10 knockdown and LRRK2 kinase inhibition potently suppress the maturation of macropinosome‐derived CCR5‐loaded signaling endosomes that are critical for CCL5‐induced immunological responses that include Akt activation and chemotaxis. These data support a novel signaling axis in the endolysosomal system whereby LRRK2‐mediated Rab10 phosphorylation stalls vesicle fast recycling to promote PI3K‐Akt immunological responses.