Engineered exosomes, derived from genetically modified cells, have shown great potential as drug delivery vehicles for treating various diseases, including cancer, cardiovascular, neurological, and immune disorders. However, systematic knowledge on optimizing drug loading and assessing delivery efficacy remains limited. This review summarizes current approaches for engineering exosomes and evaluating their drug delivery effects, as well as techniques for assessing exosome drug loading, release kinetics, cell targeting, biodistribution, pharmacokinetics, and therapeutic outcomes. It also synthesizes the latest applications of exosome engineering and drug delivery in clinical translation. Exosomes are nanoscale extracellular vesicles secreted by cells, enclosed by a lipid bilayer membrane containing various biologically active cargoes such as proteins, lipids, and nucleic acids. Engineered exosomes, generated through genetic modification of parent cells, have shown promise as drug delivery vehicles due to their high biocompatibility and low immunogenicity. However, natural exosomes have limitations such as short circulation half-lives, variability based on cell source, and insufficient drug loading capacity. To overcome these limitations, researchers have developed engineered exosomes through bioengineering techniques to enhance drug encapsulation and targeting. Exosome isolation and purification involve various techniques, including ultracentrifugation, filtration, differential centrifugation, density gradient centrifugation, immunomagnetic separation, and size exclusion chromatography. Each method has its own advantages and limitations, and the choice of method depends on the specific requirements of the study or application. The selection of an appropriate method is crucial to balance exosome purity and yield. Drug loading methods for engineered exosomes can be broadly categorized into two main technical approaches: endogenous loading and exogenous loading. Endogenous loading involves transfecting donor cells to express the desired proteins, nucleic acids, or drug molecules using genetic engineering techniques. Exogenous loading involves isolating exosomes and incorporating drugs or bioactive cargo externally using various techniques. Common exogenous loading approaches include co-incubation, electroporation, sonication, freeze-thaw cycles, and extrusion. Exosome surface decoration with targeting ligands enables directed delivery to cells expressing the cognate receptors. This includes peptide ligands, antibody fragments, aptamer ligands, and glycan-binding proteins. Modulation of endogenous proteins such as tetraspanins, integrins, and galectins can also enhance the targeting capabilities of engineered exosomes. Assessment of drug encapsulation in exosomes involves evaluating drug release efficiency, drug stability, drug delivery efficiency, cellular uptake efficiency, therapeutic efficacy, and biosafety evaluation. Various methods are employed to assess these parameters, including UV–vis spectrophotometry, high performance liquid chromatography (HPLC), fluorescence staining, and magnetic resonance imaging (MRI). Animal experiments are crucial for evaluating drug-loaded exosomes before human testing, as preclinical studies enable assessment of pharmacokinetics, dynamics, and toxicity. Animal models, such as mice and ratsEngineered exosomes, derived from genetically modified cells, have shown great potential as drug delivery vehicles for treating various diseases, including cancer, cardiovascular, neurological, and immune disorders. However, systematic knowledge on optimizing drug loading and assessing delivery efficacy remains limited. This review summarizes current approaches for engineering exosomes and evaluating their drug delivery effects, as well as techniques for assessing exosome drug loading, release kinetics, cell targeting, biodistribution, pharmacokinetics, and therapeutic outcomes. It also synthesizes the latest applications of exosome engineering and drug delivery in clinical translation. Exosomes are nanoscale extracellular vesicles secreted by cells, enclosed by a lipid bilayer membrane containing various biologically active cargoes such as proteins, lipids, and nucleic acids. Engineered exosomes, generated through genetic modification of parent cells, have shown promise as drug delivery vehicles due to their high biocompatibility and low immunogenicity. However, natural exosomes have limitations such as short circulation half-lives, variability based on cell source, and insufficient drug loading capacity. To overcome these limitations, researchers have developed engineered exosomes through bioengineering techniques to enhance drug encapsulation and targeting. Exosome isolation and purification involve various techniques, including ultracentrifugation, filtration, differential centrifugation, density gradient centrifugation, immunomagnetic separation, and size exclusion chromatography. Each method has its own advantages and limitations, and the choice of method depends on the specific requirements of the study or application. The selection of an appropriate method is crucial to balance exosome purity and yield. Drug loading methods for engineered exosomes can be broadly categorized into two main technical approaches: endogenous loading and exogenous loading. Endogenous loading involves transfecting donor cells to express the desired proteins, nucleic acids, or drug molecules using genetic engineering techniques. Exogenous loading involves isolating exosomes and incorporating drugs or bioactive cargo externally using various techniques. Common exogenous loading approaches include co-incubation, electroporation, sonication, freeze-thaw cycles, and extrusion. Exosome surface decoration with targeting ligands enables directed delivery to cells expressing the cognate receptors. This includes peptide ligands, antibody fragments, aptamer ligands, and glycan-binding proteins. Modulation of endogenous proteins such as tetraspanins, integrins, and galectins can also enhance the targeting capabilities of engineered exosomes. Assessment of drug encapsulation in exosomes involves evaluating drug release efficiency, drug stability, drug delivery efficiency, cellular uptake efficiency, therapeutic efficacy, and biosafety evaluation. Various methods are employed to assess these parameters, including UV–vis spectrophotometry, high performance liquid chromatography (HPLC), fluorescence staining, and magnetic resonance imaging (MRI). Animal experiments are crucial for evaluating drug-loaded exosomes before human testing, as preclinical studies enable assessment of pharmacokinetics, dynamics, and toxicity. Animal models, such as mice and rats