Secondary ivermectin prophylaxis for strongyloidiasis in two patients with human T-cell lymphotropic virus type 1 (HTLV-1)-associated malignancies and fully treated complicated strongyloidiasis is described. Treatment was well tolerated and neither patient developed further manifestations of hyperinfection. As treatment failure for complicated strongyloidiasis has been documented in severely immunosuppressed patients, secondary prophylaxis may be indicated.