Biodegradable, hydrophobic, and injectable liquid polymers are capable of achieving the minimally invasive, sustained, and local release of drugs. These hydrophobic injectable polymers also have potential in the area of regenerative medicine where the biomaterial should be stable for a certain period and then degrade to allow the growth of cells/tissues. This review presents exclusive coverage of biocompatible hydrophobic injectable pasty or liquid polymers that can be injected without the use of any solvent for drug delivery, tissue augmentation, and regenerative medicine application. The synthesis methodologies of several major types of hydrophobic pasty polymers used in the biomedical fields and their properties with the foremost criteria to serve as injectable biomaterial for localized drug delivery and regenerative medicine is described. The hydrophobic biodegradable injectable polymers discussed are aliphatic polyesters, polycarbonates and polyanhydrides, prepared from: lactic acid, glycolic acid, caprolactone, aliphatic diols and diacids, hydroxy fatty acids, and triglycerides such as castor oil. Liquid hydrophobic polymers are efficient to release drugs locally and have the potential in regenerative medicine due to their simple and direct injection to the required site. This review summarizes the synthetic methodologies and desired properties of biocompatible, hydrophobic, and liquid polymers that can be injected directly for the application of localized drug delivery and regenerative medicine.