Water compatible L-proline derivatives have been shown to selectively catalyze asymmetric organic reactions in water. Water-soluble benzene-1,3,5-tricarboxamide (BTA) derivatives functionalized with L-proline form supramolecular polymer organocatalysts. These polymers show high activity and selectivity as catalysts for the aldol reaction of 4-nitrobenzaldehyde and cyclohexanone in water with conversions of 94 ± 1%, d.r. of 96%, and e.r. of 99% at L-proline concentrations of only 1 mol%. Co-polymers were created by co-assembling a catalytically inactive BTA with the functionalized BTA in order to study the effect of L-proline density on catalytic activity. Finally, the importance of a hydrophobic pocket surrounding the catalytic L-proline was studied by comparing the catalytic activity of the L-proline functionalized BTA with a similarly functionalized BTA containing an additional hydrophilic ethylene glycol chain.