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We report the synthesis and characterization of sulfated pillar[5]arene hosts (P5S 2 -P5S 10 ) that differ in the number of sulfate substituents. All five P5S n hosts display high solubility in water (73-131 mM) and do not undergo significant self-association according to 1 H NMR dilution experiments. The x-ray crystal structures of P5S 6 , P5S 6  ⋅ Me 6 HDA, P5S 8  ⋅ Me 6 HDA, and P5S 10  ⋅ Me 6 HDA reveal one intracavity molecule of Me 6 HDA and several external molecules of Me 6 HDA which form a network of close methonium ⋅ ⋅ ⋅ sulfate interactions. The thermodynamic parameters of complexation between P5S n and the panel of guests was measured by direct or competitive isothermal titration calorimetry. We find that the binding free energy toward a guest becomes more negative as the number of sulfate substituents increase. Conversely, the binding free energy of a specific sulfated pillar[5]arene toward a homologous series of guests becomes more negative as the number of NMe groups increases. The ability to tune the host ⋅ guest affinity by changing the number of sulfate substituents will be valuable in supramolecular polymers, separation materials, and latching applications., (© 2024 The Author(s). Chemistry - A European Journal published by Wiley-VCH GmbH.)