Three new natural plasticizers (exudates of the Prosopis pallida and Capparis scabrida trees and gum from the Cordia lutea fruit) and polyvinyl alcohol (PVA) in different concentrations were tested to determine their influence on the properties of chitosan films prepared by a casting method. Properties such as thickness, solubility, water vapor permeability, elongation at break, tensile strength, luminosity, and anaerobic biodegradability were evaluated. Chitosan films with exudate of the Capparis scabrida tree as plasticizer had better properties than those with the other two natural plasticizers. However, the mechanical properties of the chitosan films prepared with PVA were still better than those with exudate of the Capparis scabrida tree. The films that included the three natural plasticizers in their composition were more biodegradable than those made of PVA, with films with exudate of the Capparis scabrida tree being the most biodegradable. The exudate of the Capparis scabrida tree is a potential biodegradable plasticizer for use in medical or food applications.