An object of the present invention is to provide a sewing thread treatment agent, and a sewing thread, each achieving low friction properties across a wide range of sewing speeds. As a solution, a sewing thread treatment agent is provided, which is characterized in that it contains a hydroxy-terminated polydimethylsiloxane (A), a nonionic surfactant (B), and at least one type of wax (C) selected from paraffin wax, oxidized paraffin wax, polyethylene wax, oxidized polyethylene wax, and carnauba wax.