This paper presents a PC based temperature and relative humidity monitoring system using virtual instrumentation (LabVIEW). Here I have measured the ambient temperature in degree Celsius using AD 590 IC temperature sensor. The current signal generated by the sensor and then converted to a voltage signal in the range of 0-4.5V using the signal conditioning circuit. This voltage signal is then fed to the PC using NI CARD-USB 6009. A graphical program is developed in LabVIEW to convert the received voltage signal to temperature, represent the continuous variation of temperature with voltage and also to display the ambient temperature of atmosphere. LabVIEW represents the continuous variation of relative humidity with ambient temperature graphically and theoretically using empherical equation. It also keeps record of the relative humidity and corresponding temperature, which are stored as numeric value in Excel file and perform as backup.