Disclosed is a method and apparatus for collision avoidance in a sensor network. The method includes transmitting data by a transmitter; comparing, by the transmitter, a remaining time between the data transmission and a backoff period with a turnaround time taken for the transmitter to switch from a transmit (Tx) mode to a receive (Rx) mode; selectively transmitting, by the transmitter, a busy signal indicating that a channel is in use, according to the comparison result; and receiving, by the transmitter, an acknowledgement (ACK) signal from a receiver after the turnaround time has elapsed.