Recent progress in nanostructuring and targeted doping has accelerated thermoelectric research by enabling more effective control over coupled electrical and thermal transport. In this context, transition-metal chalcogenides such as MnSe have emerged as promising candidates because their electronic structure and carrier concentration can be systematically tuned through compositional engineering to optimize transport performance. Thermoelectric power generators therefore offer a compelling, environmentally benign route for converting waste heat into electricity, operating silently and without direct pollutant emissions. This study presents a simple technique for synthesized the MnSe nanoparticles, along with an analysis of their structural, morphological, and thermoelectric characteristics. By using the hydrothermal technique to successfully synthesise the p-type pristine and MnSe nanoparticles. Various methods of characterisation including X-ray diffraction (XRD), scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDX) were used to characterize the synthesized nanoparticles. Results confirmed that nanoparticles crystalline in a cubic crystal structure with an average crystallite size 56 nm. The electrical conductivity of the MnSe material decreases as the Al content increases from 478 to 92 S/cm, primarily because of the decrease in the number of charge carriers. However, the Seebeck coefficient values are increased from 29 to 92 µV/K. The findings demonstrated a significant enhancement in the thermoelectric characteristics of MnSe nanoparticles with the introduction of Al doping, employing the hydrothermal technique. Consequently, the power factor increased from 42 to 79 µWm–1K–2, respectively. This study presents a cost-effective and efficient approach for producing a substantial amount of Al-codoped MnSe at low temperatures. The resulting material exhibits excellent thermoelectric properties, making it suitable for various practical applications.