Seaweed (Eucheuma cottonii) is one of Indonesia’s leading aquaculture commodities with high economic value. However, the post-harvest drying process still relies on conventional sun-drying methods, making production highly dependent on weather conditions and requiring a long drying duration. This study aims to design and develop a prototype seaweed dryer based on the Internet of Things (IoT) integrated with a hybrid energy system combining Solar Power Plants (PV) and the utility grid (PLN). The system utilizes an ESP32 microcontroller, DHT22 sensor, soil moisture sensor, and Automatic Transfer Switch (ATS) to ensure continuous operation. Monitoring data are displayed through Blynk, LCD, and Google Spreadsheet in real time. The prototype has a maximum capacity of 250 grams of wet seaweed. Experimental results show that the drying chamber temperature can be maintained within the range of 58–59°C while reducing air humidity from 45% to 30%. The drying process successfully reduced the seaweed weight from 250 grams to approximately 41 grams within 4 hours until reaching the target moisture content of 35%. The hybrid energy system employing a 120 Wp solar panel and a 100 Ah battery provided stable power supply during operation. The proposed system offers an effective solution to improve drying efficiency, maintain product quality, and reduce dependence on weather conditions for coastal seaweed farmers.