Plasma sphingosine-1-phosphate (S1P) regulates vascular permeability, and plasma and lymph S1P guide lymphocyte egress from lymphoid organs. S1P is made intracellularly, and little is known about how S1P is delivered into circulatory fluids. Here, we find that mice without the major facilitator superfamily transporter Spns2 have a profound reduction in lymph S1P, but only a minor decrease in plasma S1P. Spns2-deficient mice have a redistribution of lymphocytes from the spleen to lymph nodes and a loss of circulating lymphocytes, consistent with normal egress from the spleen directed by plasma S1P and blocked egress from lymph nodes directed by lymph S1P. Spns2 is needed in endothelial cells to supply lymph S1P and support lymphocyte circulation. As a differential requirement for lymph and blood S1P, Spns2 may be an attractive target for immune suppressive drugs. Display omitted ► The transporter Spns2 is required to supply lymph, but not plasma, S1P ► Spns2-deficient mice have disrupted peripheral lymphocyte circulation ► Spns2 is required in endothelial cells to secrete lymph S1P and support trafficking Blood sphingosine-1-phosphate (S1P) maintains vascular stability, and blood and lymph S1P guide lymphocyte exit from lymphoid organs. Schwab and colleagues demonstrate that while endothelial cells require the transporter Spns2 to secrete S1P into lymph, red blood cells use a Spns2-independent mechanism for S1P transport into blood. As a differential requirement for lymph and blood S1P, Spns2 may be an attractive target for immune-suppressive drugs that inhibit lymphocyte egress while minimizing vascular side effects.