Thermohygrometer is a tool that serves to measure the temperature and humidity of the room. With the existence of data storage on this tool, can help the user for monitoring the temperature and humidity of the room and can know the data previously stored so that users do not have to record the temperature and humidity data of the room at any time. When temperature and humidity are observed, the spread of nosocomial infections in the operating room can be prevented and the level of equipment damage due to temperature and humidity can be reduced. The electronic systems use microcontroller Atmega328 as main controller, SHT11 as temperature and humidity sensor, DS1307 as time marker sensor, and micro SD card as data storage. Casing of the thermohygrometer data logger was designed of akrilik and design as needed. Test instrument performed between comparator module thermohygrometer with thermohygrometer HTC-1 LCD Digital Temperature Humidity Meter. Temperature and humidity data taken in 3 conditions that is high temperature condition, medium temperature condition, cold temperature condition. Module thermohygrometer can save data every 1 minute, and data stored in the form of .txt file, with save temperature and humidity data, hour, day, date, month, years, with memory storage 8 GB. The result offield test showed that the highest standard deviation for temperature data is 1,43oC and the highest standard deviation for humidity data is 4,697%. The highest error for temperature data is 3% and the highest error for humidity data is 2,11%. Comparison of data temperature and humidity between comparator thermohygrometer with module thermohygrometer show that the modul thermohygrometer is worth it, because the result obtained are relative similiar between module and thermohygrometer. Beause, based on the PERMENKES number118/2014 abaut Kompendium Alat Kesehatan, thermohygrometer error tolerance threshold allowed is 10%