Ionic liquids (ILs) are successfully used in many fields of science, including the improvement of the performance of ion-selective sensors based on plasticized polymer matrices. However, the use of ionic liquids in optical sensors has not been sufficiently studied. In this paper, we study how the gradual replacement of the conventional plasticizer in the composition of the polymer optode matrix with an ionic liquid affects the characteristics of the optode response. The shift of the dynamic range of the sensor caused by a decrease in the ion exchange constant upon the addition of ionic liquid is demonstrated. The possibility of using ionic liquids to create a sensor of individual ionic activity is also shown.