The fluorescent photoinduced electron transfer (PET) chemosensors 1−3 were synthesized fromcholic acid. 1 and 2 containing amidothiourea groups as anion receptive sites demonstrated muchhigher affinity toward anions than 3 containing traditional thiourea H-bond donating group.Comparative studies on their binding affinity toward carboxylates, dihydrogen phosphate, andhalides revealed that the amidothiourea moiety on the C17 side chain could work cooperativelywith H-bond donating groups on C7 and C12 to bind spherical halogen anions. An unexpectedspecific fluorescence enhancement of 1 by coordinating bromide ion was observed.