Every year, the influenza virus infection causes significant morbidity and mortality due to its high contagiousness and ease of spread. The influenza virus family consists of four subtypes: A, B, C, and D. Both types of influenza viruses A and B cause outbreaks of disease in humans almost every winter throughout the world (known as flu season). So, their spreading must be controlled by using antiviral drugs such as oseltamivir phosphate (OSP). This drug is sold under the trade name “Tamiflu®" for the treatment of influenza infection. In this comprehensive review, multiple analytical techniques for quantifying OSP were used—including capillary electrophoresis, spectrophotometric analysis (UV, colorimetric and spectrofluorometric), electrochemical methods, HPLC, and LC-MS/MS—to quantify OSP in fixed-dose pharmaceutical dosage forms and other matrices such as human and animal plasma, saliva and urine. The data presented in this review paper can be used to successfully conduct additional analytical research for estimating OSP.