Although evolving technology enables the production of sensors with excellent properties, the development of a fast-response, portable, and low-cost sensor is very important for food detection and also for disease diagnosis. Herein, zinc doped manganese oxide nanocomposites (Zn:MnO₂ NCs) were designed as smartphone-integrated colorimetric and non-enzymatic electrochemical sensors with high sensitivity and selectivity. According to the Transmission electron microscopy (TEM) results showed that the Zn:MnO₂ NCs had a spherical shape with a uniform particle size of less than 10 nm. As one of the most important results, the colorimetric sensing behavior of the Zn:MnO₂ NCs was showed excellent fast and selective sensitivity against dopamine, ascorbic acid, gallic acid, and tannic acid among the various bio-analytes such as sugars, amino acids, hormones, and phenolic compounds. The Zn:MnO₂ NCs were successfully used as smartphone supported paper based sensor against dopamine, gallic acid, and tannic acid using RGB analysis and with low limit of detection (LOD) values of 2.89, 3.88, and 7.81 μM, respectively. Moreover, Zn:MnO₂ exhibited excellent a non-enzymatic electrochemical sensor performance against ascorbic acid with a low LOD of 239 nM and high sensitivity of 44.73 μA/cm² mM in a concentration range of 0.52–11.35 mM. These findings emphasize that the designed Zn:MnO₂ NCs based sensors has a potential as easily applicable and rapid sensor systems against of ascorbic acid, gallic acid, tannic acid and dopamine for real food and blood samples that as a point-of-care detection systems.