This paper proposes a 900 MHz RFID passive tag embedded in T-shirts using conductive ink. The tag antenna size was $105.42;mm{ imes}27.58;mm$and simulated using MWS 2009 (CST Co.). It fabricated using a silk screen method. The tag antenna consisted of a loop part to match the imaginary value of the RFID Chip impedance, an antenna part to match real value of the RFID Chip impedance and a RFID chip bonding part. The operating frequency bandwidth at -3 dB of return loss was between 790 and 945 MHz and could be used in Europe, Middle Asia, China, Korea, and North America. The average sensitivity measured between 860 and 960 MHz was -9.96 dBm and the maximum reading range was 2.3 m. These parameters were measured at the Songdo RFID/USN Center. When wearing a T-shirt with the tag, the measured reading distance was approximately 2.0 m. The tag showed some problems in cases of washing, exposure to sunlight, ironing and wrinkling but it had satisfactory electrical properties such sensitivity, reading range and operating bandwidth.