The work deals with synthesizing carbon-based nanomaterial, i.e., graphitic carbon nitride, which was carried out using the high-temperature condensation method. Graphitic carbon nitride is characterized by cost efficiency, increased thermal resilience, a two-dimensional molecular layer structure, biocompatibility and stability. These properties can be used in the electrochemical investigations of fungicides such as dichlorophen and thymol. The synthesized nanomaterial was first characterized using XRD, SEM, UV-DRS, BET, FTIR, CV and EIS investigations. The cyclic voltammetry behavior of dichlorophen and thymol shows the proton-coupled irreversible electron transfer process at a modified carbon paste electrode with the participation of same number of protons and electrons. The developed sensor exhibited good detection limits for the dichlorophen and thymol as low as 15.3 nM and 12.0 nM with the sensitivity of 126.8 µA·µM−1·cm−2 and 59.2 µA·µM−1·cm−2, respectively. The applicability of the developed sensor was tested in spiked soil and water samples, and good recoveries were achieved with a% RSD of 1.67 and 1.30, respectively. The anti-interference responses to metal ions demonstrate the selectivity (qualitative) of the developed sensor in the electrochemical detection of dichlorophen and thymol. In the future, the sensor developed would offer the potential to sensitively and selectively detect other pesticide molecules in environmental samples.