The identification of secreted proteins in cell culture supernatants is a useful method for the noninvasive evaluation of cultured cells. Herein, we show that a fingerprint-based sensor technique can be used to identify typical hepatocyte-derived secretory proteins spiked into a cell culture medium. A poly-L-lysine modified with environment-sensitive dansyl groups (PLL-Dnc), which allows a turn-on fluorescent response with cross-reactivity against different analytes, was employed for the sensing of a series of secretory proteins (albumin, α1-antitrypsin, fibrinogen, transferrin, and α-fetoprotein). An array of PLL-Dnc in different buffer solutions successfully produced fluorescence fingerprints as a result of distinct interactions with analyte proteins depending on solution conditions (pH and ionic strength), enabling the qualitative identification of five secretory proteins in culture media (40 μg/mL) with 100% accuracy using linear discriminant analysis. The array system was also capable of analyzing culture media that contain different concentrations of albumin and α-fetoprotein under realistic conditions. This work demonstrates the solution-condition-dependent discriminatory response of PLL-Dnc toward proteins spiked into a culture medium, rendering such a PLL-Dnc system a promising platform for the antibody-free and marker-based evaluation of cultured cells.