To search for effective and selective inhibitors of carboxylesterase (CES), a series of 3-oxo-2-tolylhydrazinylidene-4,4,4-trifluorobutanoates bearing higher or natural alcohol moieties was synthesized via pre-transesterification of ethyl trifluoroacetylacetate with alcohols to isolate transesterificated oxoesters as lithium salts, which were then subjected to azo coupling with tolyldiazonium chloride. Inhibitory activity against porcine liver CES, along with two structurally related serine hydrolases, acetylcholinesterase and butyrylcholinesterase, were investigated using enzyme kinetics and molecular docking. Kinetics studies demonstrated that the tested keto-esters are reversible and selective mixed-type CES inhibitors. Analysis of X-ray crystallographic data together with our IR and NMR spectra and QM calculations indicated that the Z-isomers were the most stable. The kinetic data were well explained by the molecular docking results of the Z-isomers, which showed specific binding of the compounds in the CES catalytic active site with carbonyl oxygen atoms in the oxyanion hole and non-specific binding outside it. Some compounds were studied as inhibitors of the main human isozymes involved in biotransformation of ester-containing drugs, hCES1 and hCES2. Esters of geraniol (3d) and adamantol (3e) proved to be highly active and selective inhibitors of hCES2, inhibiting the enzyme in the nanomolar range, whereas esters of borneol (3f) and isoborneol (3g) were more active and selective against hCES1. Computational ADMET studies revealed that all test compounds had excellent intestinal absorption, medium blood-brain barrier permeability, and low hERG liability risks. Moreover, all test compounds possessed radical-scavenging properties and low acute toxicity. Overall, the results indicate that members of this novel series of esters have the potential to be good candidates as hCES1 or hCES2 inhibitors for biomedicinal applications.